How is radiation therapy tolerated? Radiation therapy in oncology

• Introduction
• external beam radiation therapy
• Electronic therapy
• Brachytherapy
• Open sources of radiation
• Total body irradiation

Introduction

Radiation therapy - a method of treatment malignant tumors ionizing radiation. The most commonly used remote therapy is high-energy x-rays. This method of treatment has been developed over the past 100 years, it has been significantly improved. It is used in the treatment of more than 50% of cancer patients, it plays the most important role among non-surgical treatments for malignant tumors.

A brief excursion into history

1896 Discovery of X-rays.

1898 Discovery of radium.

1899 Successful treatment of skin cancer with x-rays. 1915 Treatment of a neck tumor with a radium implant.

1922 Cure of cancer of the larynx with X-ray therapy. 1928 The X-ray was adopted as the unit of radiation exposure. 1934 The principle of radiation dose fractionation was developed.

1950s. Teletherapy with radioactive cobalt (energy 1 MB).

1960s. Obtaining megavolt x-ray radiation using linear accelerators.

1990s. 3D planning radiotherapy. When X-rays pass through living tissue, the absorption of their energy is accompanied by ionization of molecules and the appearance of fast electrons and free radicals. The most important biological effect of X-rays is DNA damage, in particular, the breaking of bonds between its two helical strands.

The biological effect of radiation therapy depends on the dose of radiation and the duration of therapy. Early clinical researches The results of radiotherapy showed that daily exposure to relatively small doses allows the use of a higher total dose, which, when applied to the tissues at once, is unsafe. Fractionation of the radiation dose can significantly reduce the radiation load on normal tissues and achieve the death of tumor cells.

Fractionation is the division of the total dose for external beam radiation therapy into small (usually single) daily doses. It ensures the preservation of normal tissues and preferential damage to tumor cells and allows you to use a higher total dose without increasing the risk to the patient.

Radiobiology of normal tissue

The effect of radiation on tissues is usually mediated by one of the following two mechanisms:

• loss of mature functionally active cells as a result of apoptosis (programmed cell death, usually occurring within 24 hours after irradiation);
• loss of the ability of cells to divide

Usually these effects depend on the radiation dose: the higher it is, the more cells die. However, the radiosensitivity of different types of cells is not the same. Some types of cells respond to irradiation predominantly by initiating apoptosis, these are hematopoietic cells and cells salivary glands. Most tissues or organs have a significant reserve of functionally active cells, so the loss of even a small part of these cells as a result of apoptosis is not clinically manifested. Typically, lost cells are replaced by progenitor or stem cell proliferation. These may be cells that survived after tissue irradiation or migrated into it from non-irradiated areas.

Radiosensitivity of normal tissues

• High: lymphocytes, germ cells
• Moderate: epithelial cells.
• Resistance, nerve cells, connective tissue cells.

In cases where a decrease in the number of cells occurs as a result of the loss of their ability to proliferate, the rate of renewal of the cells of the irradiated organ determines the time during which tissue damage appears and which can vary from several days to a year after irradiation. This served as the basis for dividing the effects of irradiation into early, or acute, and late. Changes that develop during the period of radiation therapy up to 8 weeks are considered acute. Such a division should be considered arbitrary.

Acute changes with radiation therapy

Acute changes affect mainly the skin, mucous membrane and hematopoietic system. Despite the fact that the loss of cells during irradiation initially occurs in part due to apoptosis, the main effect of irradiation is manifested in the loss of the reproductive ability of cells and the disruption of the replacement of dead cells. Therefore, the earliest changes appear in tissues characterized by an almost normal process of cell renewal.

The timing of the manifestation of the effect of irradiation also depends on the intensity of irradiation. After simultaneous irradiation of the abdomen at a dose of 10 Gy, the death and desquamation of the intestinal epithelium occurs within several days, while when this dose is fractionated with a daily dose of 2 Gy, this process is extended for several weeks.

The speed of recovery processes after acute changes depends on the degree of reduction in the number of stem cells.

Acute changes during radiation therapy:

• develop within B weeks after the start of radiation therapy;
• skin suffer. Gastrointestinal tract, bone marrow;
• the severity of changes depends on the total dose of radiation and the duration of radiation therapy;
• therapeutic doses are selected in such a way as to achieve complete restoration of normal tissues.

Late Changes After Radiation Therapy

Late changes occur mainly in tissues and organs whose cells are characterized by slow proliferation (for example, lungs, kidneys, heart, liver and nerve cells), but are not limited to them. For example, in the skin, in addition to the acute reaction of the epidermis, later changes may develop after a few years.

The distinction between acute and late changes is important from a clinical point of view. Since acute changes also occur with traditional radiation therapy with dose fractionation (approximately 2 Gy per fraction 5 times a week), if necessary (development of an acute radiation reaction), it is possible to change the fractionation regimen, distributing the total dose over a longer period in order to save more stem cells. As a result of proliferation, the surviving stem cells will repopulate the tissue and restore its integrity. With a relatively short duration of radiation therapy, acute changes may occur after its completion. This does not allow for adjustment of the fractionation regimen based on the severity of the acute reaction. If intensive fractionation causes a decrease in the number of surviving stem cells below the level required for effective tissue repair, acute changes can become chronic.

According to the definition, late radiation reactions appear only after long time after irradiation, and acute changes do not always make it possible to predict chronic reactions. Although the total dose of radiation plays a leading role in the development of a late radiation reaction, an important place also belongs to the dose corresponding to one fraction.

Late changes after radiotherapy:

• lungs, kidneys, central nervous system (CNS), heart, connective tissue suffer;
• the severity of the changes depends on the total radiation dose and the radiation dose corresponding to one fraction;
• recovery does not always occur.

Radiation changes in individual tissues and organs

Skin: acute changes.

• Erythema, resembling a sunburn: appears in the 2-3rd week; patients note burning, itching, soreness.
• Desquamation: first note the dryness and desquamation of the epidermis; later weeping appears and the dermis is exposed; usually within 6 weeks after completion of radiation therapy, the skin heals, residual pigmentation fades within a few months.
• When the healing process is inhibited, ulceration occurs.

Skin: late changes.

• Atrophy.
• Fibrosis.
• Telangiectasia.

The mucous membrane of the oral cavity.

• Erythema.
• Painful ulcers.
• Ulcers usually heal within 4 weeks after radiation therapy.
• Dryness may occur (depending on the dose of radiation and the mass of salivary gland tissue exposed to radiation).

Gastrointestinal tract.

• Acute mucositis, which manifests itself after 1-4 weeks with symptoms of a lesion of the gastrointestinal tract that has been exposed to radiation.
• Esophagitis.
• Nausea and vomiting (involvement of 5-HT 3 receptors) - with irradiation of the stomach or small intestine.
• Diarrhea - with irradiation of the colon and distal small intestine.
• Tenesmus, secretion of mucus, bleeding - with irradiation of the rectum.
• Late changes - ulceration of the mucous membrane, fibrosis, intestinal obstruction, necrosis.

central nervous system

• There is no acute radiation reaction.
• Late radiation reaction develops after 2-6 months and is manifested by symptoms caused by demyelination: brain - drowsiness; spinal cord - Lermitte's syndrome (shooting pain in the spine, radiating to the legs, sometimes provoked by flexion of the spine).
• 1-2 years after radiation therapy, necrosis may develop, leading to irreversible neurological disorders.

Lungs.

• Acute symptoms of airway obstruction are possible after a single exposure at a high dose (eg, 8 Gy).
• After 2-6 months, radiation pneumonitis develops: cough, dyspnea, reversible changes on radiographs chest; may improve with the appointment of glucocorticoid therapy.
• After 6-12 months, the development of irreversible pulmonary fibrosis of the kidneys is possible.
• There is no acute radiation reaction.
• The kidneys are characterized by a significant functional reserve, so a late radiation reaction can develop even after 10 years.
• Radiation nephropathy: proteinuria; arterial hypertension; kidney failure.

Heart.

• Pericarditis - after 6-24 months.
• After 2 years or more, the development of cardiomyopathy and conduction disturbances is possible.

Tolerance of normal tissues to repeated radiotherapy

Recent studies have shown that some tissues and organs have a pronounced ability to recover from subclinical radiation damage, which makes it possible, if necessary, to carry out repeated radiation therapy. Significant regeneration capabilities inherent in the CNS make it possible to repeatedly irradiate the same areas of the brain and spinal cord and to achieve clinical improvement in the recurrence of tumors localized in or near critical zones.

Carcinogenesis

DNA damage caused by radiation therapy can lead to the development of a new malignant tumor. It can appear 5-30 years after irradiation. Leukemia usually develops after 6-8 years, solid tumors - after 10-30 years. Some organs are more prone to secondary cancer, especially if radiation therapy was given in childhood or adolescence.

• Secondary cancer induction is a rare but serious consequence of radiation exposure characterized by a long latent period.
• In cancer patients, the risk of induced cancer recurrence should always be weighed.

Repair of damaged DNA

For some DNA damage caused by radiation, repair is possible. When bringing to the tissues more than one fractional dose per day, the interval between fractions should be at least 6-8 hours, otherwise massive damage to normal tissues is possible. There are a number of hereditary defects in the DNA repair process, and some of them predispose to the development of cancer (for example, in ataxia-telangiectasia). Conventional radiation therapy used to treat tumors in these patients can cause severe reactions in normal tissues.

hypoxia

Hypoxia increases the radiosensitivity of cells by 2-3 times, and in many malignant tumors there are areas of hypoxia associated with impaired blood supply. Anemia enhances the effect of hypoxia. With fractionated radiation therapy, the reaction of the tumor to radiation can manifest itself in the reoxygenation of hypoxic areas, which can enhance its detrimental effect on tumor cells.

Fractionated Radiation Therapy

Target

To optimize remote radiation therapy, it is necessary to choose the most advantageous ratio of its following parameters:

• total radiation dose (Gy) to achieve the desired therapeutic effect;
• the number of fractions into which the total dose is distributed;
• the total duration of radiotherapy (defined by the number of fractions per week).

Linear quadratic model

When irradiated at doses accepted in clinical practice, the number of dead cells in tumor tissue and tissues with rapidly dividing cells is linearly dependent on the dose of ionizing radiation (the so-called linear, or α-component of the irradiation effect). In tissues with a minimal cell turnover rate, the effect of radiation is largely proportional to the square of the dose delivered (the quadratic, or β-component, of the effect of radiation).

An important consequence follows from the linear-quadratic model: with fractionated irradiation of the affected organ with small doses, changes in tissues with a low cell renewal rate (late-reacting tissues) will be minimal, in normal tissues with rapidly dividing cells, damage will be insignificant, and in tumor tissue it will be the greatest. .

Fractionation mode

Typically, the tumor is irradiated once a day from Monday to Friday. Fractionation is carried out mainly in two modes.

Short-term radiation therapy with large fractional doses:

• Advantages: a small number of irradiation sessions; saving resources; rapid tumor damage; lower probability of repopulation of tumor cells during the treatment period;
• Flaws: limited opportunity increasing the safe total dose of radiation; relatively high risk of late damage in normal tissues; reduced possibility of reoxygenation of tumor tissue.

Long-term radiation therapy with small fractional doses:

• Advantages: less pronounced acute radiation reactions (but a longer duration of treatment); less frequency and severity of late lesions in normal tissues; the possibility of maximizing the safe total dose; the possibility of maximum reoxygenation of the tumor tissue;
• Disadvantages: great burden for the patient; a high probability of repopulation of cells of a rapidly growing tumor during the treatment period; long duration of acute radiation reaction.

Radiosensitivity of tumors

For radiation therapy of some tumors, in particular lymphoma and seminoma, radiation in a total dose of 30-40 Gy is sufficient, which is approximately 2 times less than the total dose required for the treatment of many other tumors (60-70 Gy). Some tumors, including gliomas and sarcomas, may be resistant to the highest doses that can be safely delivered to them.

Tolerated doses for normal tissues

Some tissues are especially sensitive to radiation, so the doses applied to them must be relatively low in order to prevent late damage.

If the dose corresponding to one fraction is 2 Gy, then the tolerant doses for various organs will be as follows:

• testicles - 2 Gy;
• lens - 10 Gy;
• kidney - 20 Gy;
• light - 20 Gy;
• spinal cord - 50 Gy;
• brain - 60 Gr.

At doses higher than those indicated, the risk of acute radiation injury increases dramatically.

Intervals between factions

After radiation therapy, some of the damage caused by it is irreversible, but some is reversed. When irradiated with one fractional dose per day, the repair process until irradiation with the next fractional dose is almost completely completed. If more than one fractional dose per day is applied to the affected organ, then the interval between them should be at least 6 hours so that as many damaged normal tissues as possible can be restored.

Hyperfractionation

When summing up several fractional doses less than 2 Gy, the total radiation dose can be increased without increasing the risk of late damage in normal tissues. To avoid an increase in the total duration of radiation therapy, weekends should also be used or more than one fractional dose per day should be used.

According to one randomized controlled trial conducted in patients with small cell lung cancer, the CHART (Continuous Hyperfractionated Accelerated Radio Therapy) regimen, in which a total dose of 54 Gy was administered in fractional doses of 1.5 Gy 3 times a day for 12 consecutive days, was found to be more effective than the traditional scheme of radiation therapy with a total dose of 60 Gy divided into 30 fractions with a treatment duration of 6 weeks. There was no increase in the frequency of late lesions in normal tissues.

Optimal radiotherapy regimen

The choice of radiotherapy regimen is guided by clinical features disease in each case. Radiation therapy is generally divided into radical and palliative.

radical radiotherapy.

• Usually carried out with the maximum tolerated dose for the complete destruction of tumor cells.
• Lower doses are used to irradiate tumors characterized by high radiosensitivity, and to kill cells of a microscopic residual tumor with moderate radiosensitivity.
• Hyperfractionation in a total daily dose of up to 2 Gy minimizes the risk of late radiation damage.
• A severe acute toxic reaction is acceptable, given the expected increase in life expectancy.
• Typically, patients are able to undergo radiation sessions daily for several weeks.

Palliative radiotherapy.

• The purpose of such therapy is to quickly alleviate the patient's condition.
• Life expectancy does not change or increases slightly.
• The lowest doses and fractions to achieve the desired effect are preferred.
• Prolonged acute radiation damage to normal tissues should be avoided.
• Late radiation damage to normal tissues has no clinical significance.

external beam radiation therapy

Basic principles

Treatment with ionizing radiation generated by an external source is known as external beam radiation therapy.

Superficially located tumors can be treated with low voltage x-rays (80-300 kV). The electrons emitted by the heated cathode are accelerated in the x-ray tube and. hitting the tungsten anode, they cause X-ray bremsstrahlung. The dimensions of the radiation beam are selected using metal applicators of various sizes.

For deep-seated tumors, megavolt x-rays are used. One of the options for such radiation therapy involves the use of cobalt 60 Co as a radiation source, which emits γ-rays with an average energy of 1.25 MeV. To obtain a sufficiently high dose, a radiation source with an activity of approximately 350 TBq is needed.

However, linear accelerators are used much more often to obtain megavolt X-rays; in their waveguide, electrons are accelerated almost to the speed of light and directed to a thin, permeable target. The energy of the resulting X-ray bombardment ranges from 4 to 20 MB. Unlike 60 Co radiation, it is characterized by greater penetrating power, higher dose rate, and better collimation.

The design of some linear accelerators makes it possible to obtain electron beams of various energies (usually in the range of 4-20 MeV). With the help of X-ray radiation obtained in such installations, it is possible to evenly affect the skin and tissues located under it to the desired depth (depending on the energy of the rays), beyond which the dose decreases rapidly. Thus, the depth of exposure at an electron energy of 6 MeV is 1.5 cm, and at an energy of 20 MeV it reaches approximately 5.5 cm. Megavolt radiation is an effective alternative to kilovoltage radiation in the treatment of superficially located tumors.

The main disadvantages of low-voltage radiotherapy:

• high dose of radiation to the skin;
• relatively rapid decrease in dose as it penetrates deeper;
• higher dose absorbed by bones compared to soft tissues.

Features of megavolt radiotherapy:

• distribution of the maximum dose in the tissues located under the skin;
• relatively little damage to the skin;
• exponential relationship between absorbed dose reduction and penetration depth;
• a sharp decrease in the absorbed dose beyond the specified irradiation depth (penumbra zone, penumbra);
• the ability to change the shape of the beam using metal screens or multileaf collimators;
• the possibility of creating a dose gradient across the beam cross section using wedge-shaped metal filters;
• the possibility of irradiation in any direction;
• the possibility of bringing a larger dose to the tumor by cross-irradiation from 2-4 positions.

Radiotherapy planning

Preparation and implementation of external beam radiation therapy includes six main stages.

Beam dosimetry

Before starting the clinical use of linear accelerators, their dose distribution should be established. Given the characteristics of the absorption of high-energy radiation, dosimetry can be performed using small dosimeters with an ionization chamber placed in a tank of water. It is also important to measure the calibration factors (known as exit factors) that characterize the exposure time for a given absorption dose.

computer planning

For simple planning, you can use tables and graphs based on the results of beam dosimetry. But in most cases, computers with special software are used for dosimetric planning. The calculations are based on the results of beam dosimetry, but also depend on algorithms that take into account the attenuation and scattering of X-rays in tissues of different densities. These tissue density data are often obtained using CT performed in the position of the patient in which he will be in radiation therapy.

Target Definition

The most important step in radiotherapy planning is the definition of the target, i.e. volume of tissue to be irradiated. This volume includes the volume of the tumor (determined visually during clinical examination or by CT) and the volume of adjacent tissues, which may contain microscopic inclusions of tumor tissue. It is not easy to determine the optimal target boundary (planned target volume), which is associated with a change in the position of the patient, movement internal organs and the need to recalibrate the apparatus in connection with this. It is also important to determine the position of critical organs, i.e. organs characterized by low tolerance to radiation (for example, spinal cord, eyes, kidneys). All this information is entered into the computer along with CT scans that completely cover the affected area. In relatively uncomplicated cases, the volume of the target and the position of critical organs are determined clinically using conventional radiographs.

Dose planning

The goal of dose planning is to achieve a uniform distribution of the effective dose of radiation in the affected tissues so that the dose to critical organs does not exceed their tolerable dose.

The parameters that can be changed during irradiation are as follows:

• beam dimensions;
• beam direction;
• number of bundles;
• relative dose per beam (“weight” of the beam);
• dose distribution;
• use of compensators.

Treatment Verification

It is important to direct the beam correctly and not cause damage to critical organs. For this, radiography on a simulator is usually used before radiation therapy, it can also be performed in the treatment of megavoltage x-ray machines or electronic portal imaging devices.

Choice of radiotherapy regimen

The oncologist determines the total radiation dose and draws up a fractionation regimen. These parameters, together with the parameters of the beam configuration, fully characterize the planned radiation therapy. This information is entered into a computer verification system that controls the implementation of the treatment plan on a linear accelerator.

New in radiotherapy

3D planning

Perhaps the most significant development in the development of radiotherapy over the past 15 years has been the direct application of scanning methods of research (most often CT) for topometry and radiation planning.

Computed tomography planning has a number of significant advantages:

• the possibility of more exact definition localization of the tumor and critical organs;
• more accurate dose calculation;
• true 3D planning capability to optimize treatment.

Conformal beam therapy and multileaf collimators

The goal of radiotherapy has always been to deliver a high dose of radiation to a clinical target. For this, irradiation with a rectangular beam was usually used with limited use of special blocks. Part of the normal tissue was inevitably irradiated with a high dose. By placing blocks of a certain shape, made of a special alloy, in the path of the beam and using the capabilities of modern linear accelerators, which have appeared due to the installation of multileaf collimators (MLC) on them. it is possible to achieve a more favorable distribution of the maximum radiation dose in the affected area, i.e. increase the level of conformity of radiation therapy.

The computer program provides such a sequence and amount of displacement of the petals in the collimator, which allows you to get the beam of the desired configuration.

By minimizing the volume of normal tissues receiving a high dose of radiation, it is possible to achieve a distribution of a high dose mainly in the tumor and avoid an increase in the risk of complications.

Dynamic and Intensity-Modulated Radiation Therapy

Using the standard method of radiation therapy, it is difficult to effectively influence the target, which has an irregular shape and is located near critical organs. In such cases, dynamic radiation therapy is used when the device rotates around the patient, continuously emitting X-rays, or the intensity of beams emitted from stationary points is modulated by changing the position of the collimator blades, or both methods are combined.

Electronic therapy

Despite the fact that electron radiation is equivalent to photon radiation in terms of radiobiological action on normal tissues and tumors, physical characteristics electron beams have some advantages over photon beams in the treatment of tumors located in certain anatomical regions. Unlike photons, electrons have a charge, so when they penetrate tissue, they often interact with it and, losing energy, cause certain consequences. Irradiation of tissue below a certain level is negligible. This makes it possible to irradiate a tissue volume to a depth of several centimeters from the skin surface without damaging the underlying critical structures.

Comparative Features of Electron and Photon Beam Therapy Electron Beam Therapy:

• limited depth of penetration into tissues;
• the radiation dose outside the useful beam is negligible;
• especially indicated for superficial tumors;
• eg skin cancer, head and neck tumors, breast cancer;
• the dose absorbed by normal tissues (eg, spinal cord, lung) underlying the target is negligible.

Photon beam therapy:

• high penetrating power of photon radiation, which allows treating deep-seated tumors;
• minimal skin damage;
• Beam features allow better matching with the geometry of the irradiated volume and facilitate cross-irradiation.

Generation of electron beams

Most radiotherapy centers are equipped with high-energy linear accelerators capable of generating both X-rays and electron beams.

Since electrons are subject to significant scattering when passing through air, a guide cone, or trimmer, is placed on the radiation head of the apparatus to collimate the electron beam near the surface of the skin. Further correction of the electron beam configuration can be done by attaching a lead or cerrobend diaphragm to the end of the cone, or by covering the normal skin around the affected area with lead rubber.

Dosimetric characteristics of electron beams

The impact of electron beams on a homogeneous tissue is described by the following dosimetric characteristics.

Dose versus penetration depth

The dose gradually increases to a maximum value, after which it sharply decreases to almost zero at a depth equal to the usual depth of penetration of electron radiation.

Absorbed dose and radiation flux energy

The typical penetration depth of an electron beam depends on the energy of the beam.

The surface dose, which is usually characterized as the dose at a depth of 0.5 mm, is much higher for an electron beam than for megavolt photon radiation, and ranges from 85% of the maximum dose at low energy levels (less than 10 MeV) to approximately 95% of the maximum dose at high energy level.

At accelerators capable of generating electron radiation, the radiation energy level varies from 6 to 15 MeV.

Beam profile and penumbra zone

The penumbra zone of the electron beam turns out to be somewhat larger than that of the photon beam. For an electron beam, the dose reduction to 90% of the central axial value occurs approximately 1 cm inward from the conditional geometric boundary of the irradiation field at a depth where the dose is maximum. For example, a beam with a cross section of 10x10 cm 2 has an effective irradiation field size of only Bx8 cm. The corresponding distance for the photon beam is only approximately 0.5 cm. Therefore, to irradiate the same target in the clinical dose range, it is necessary that the electron beam has a larger cross section. This feature of electron beams makes it problematic to pair photon and electron beams, since it is impossible to ensure dose uniformity at the boundary of irradiation fields at different depths.

Brachytherapy

Brachytherapy is a type of radiation therapy in which a radiation source is placed in the tumor itself (the amount of radiation) or near it.

Indications

Brachytherapy is performed in cases where it is possible to accurately determine the boundaries of the tumor, since the irradiation field is often selected for a relatively small volume of tissue, and leaving a part of the tumor outside the irradiation field carries a significant risk of recurrence at the border of the irradiated volume.

Brachytherapy is applied to tumors, the localization of which is convenient both for the introduction and optimal positioning of radiation sources, and for its removal.

Advantages

Increasing the radiation dose increases the efficiency of suppression of tumor growth, but at the same time increases the risk of damage to normal tissues. Brachytherapy allows you to bring a high dose of radiation to a small volume, limited mainly by the tumor, and increase the effectiveness of the impact on it.

Brachytherapy generally does not last long, usually 2-7 days. Continuous low-dose irradiation provides a difference in the rate of recovery and repopulation of normal and tumor tissues, and, consequently, a more pronounced destructive effect on tumor cells, which increases the effectiveness of treatment.

Cells that survive hypoxia are resistant to radiation therapy. Low-dose irradiation during brachytherapy promotes tissue reoxygenation and increases the radiosensitivity of tumor cells that were previously in a state of hypoxia.

The distribution of radiation dose in a tumor is often uneven. When planning radiation therapy, care should be taken to ensure that the tissues around the boundaries of the radiation volume receive the minimum dose. The tissue near the radiation source in the center of the tumor often receives twice the dose. Hypoxic tumor cells are located in avascular zones, sometimes in foci of necrosis in the center of the tumor. Therefore, a higher dose of irradiation of the central part of the tumor negates the radioresistance of the hypoxic cells located here.

At irregular shape tumor rational positioning of radiation sources avoids damage to the normal critical structures and tissues located around it.

Flaws

Many of the radiation sources used in brachytherapy emit γ-rays, and medical personnel are exposed to radiation. Although the doses of radiation are small, this circumstance should be taken into account. The exposure of medical personnel can be reduced by using low activity radiation sources and their automated introduction.

Patients with large tumors are not suitable for brachytherapy. however, it can be used as an adjuvant treatment after external beam radiation therapy or chemotherapy when the size of the tumor becomes smaller.

The dose of radiation emitted by a source decreases in proportion to the square of the distance from it. Therefore, in order to irradiate the intended volume of tissue adequately, it is important to carefully calculate the position of the source. The spatial arrangement of the radiation source depends on the type of applicator, the location of the tumor, and what tissues surround it. Correct positioning of the source or applicators requires special skills and experience and is therefore not possible everywhere.

Surrounding structures such as The lymph nodes with obvious or microscopic metastases, are not subject to irradiation with radiation sources implanted or introduced into the cavity.

Varieties of brachytherapy

Intracavitary - a radioactive source is injected into any cavity located inside the patient's body.

Interstitial - a radioactive source is injected into tissues containing a tumor focus.

Surface - a radioactive source is placed on the surface of the body in the affected area.

The indications are:

• skin cancer;
• eye tumors.

Radiation sources can be entered manually and automatically. Manual insertion should be avoided whenever possible, as it exposes medical personnel to radiation hazards. The source is injected through injection needles, catheters or applicators, which are previously embedded in the tumor tissue. The installation of "cold" applicators is not associated with irradiation, so you can slowly choose the optimal geometry of the irradiation source.

Automated introduction of radiation sources is carried out using devices, such as "Selectron", commonly used in the treatment of cervical cancer and endometrial cancer. This method consists in the computerized delivery of stainless steel pellets, containing, for example, cesium in glasses, from a leaded container into applicators inserted into the uterine or vaginal cavity. This completely eliminates the exposure of the operating room and medical personnel.

Some automated injection devices work with high-intensity radiation sources, such as Microselectron (iridium) or Cathetron (cobalt), the treatment procedure takes up to 40 minutes. In low dose brachytherapy, the radiation source must be left in the tissues for many hours.

In brachytherapy, most radiation sources are removed after exposure to the calculated dose has been achieved. However, there are also permanent sources, they are injected into the tumor in the form of granules and after their exhaustion they are no longer removed.

Radionuclides

Sources of y-radiation

Radium has been used as a source of y-radiation in brachytherapy for many years. It is currently out of use. The main source of y-radiation is the gaseous daughter product of the decay of radium, radon. Radium tubes and needles must be sealed and checked for leakage frequently. The γ-rays emitted by them have a relatively high energy (on average 830 keV), and a rather thick lead shield is needed to protect against them. During the radioactive decay of cesium, gaseous daughter products are not formed, its half-life is 30 years, and the energy of y-radiation is 660 keV. Cesium has largely replaced radium, especially in gynecological oncology.

Iridium is produced in the form of soft wire. It has a number of advantages over traditional radium or cesium needles for interstitial brachytherapy. thin wire(0.3 mm diameter) can be inserted into a flexible nylon tube or hollow needle previously inserted into the tumor. A thicker hairpin-shaped wire can be directly inserted into the tumor using a suitable sheath. In the US, iridium is also available for use in the form of pellets encapsulated in a thin plastic shell. Iridium emits γ-rays with an energy of 330 keV, and a 2-cm-thick lead screen makes it possible to reliably protect medical personnel from them. The main drawback of iridium is its relatively short half-life (74 days), which requires a fresh implant to be used in each case.

The isotope of iodine, which has a half-life of 59.6 days, is used as a permanent implant in prostate cancer. The γ-rays it emits are of low energy and, since the radiation emitted from patients after implantation of this source is negligible, patients can be discharged early.

Sources of β-radiation

Plates that emit β-rays are mainly used in the treatment of patients with eye tumors. Plates are made of strontium or ruthenium, rhodium.

dosimetry

The radioactive material is implanted into tissues in accordance with the radiation dose distribution law, which depends on the system used. In Europe, the classic Parker-Paterson and Quimby implant systems have been largely superseded by the Paris system, particularly suited to iridium wire implants. In dosimetric planning, a wire with the same linear radiation intensity is used, radiation sources are placed in parallel, straight, on equidistant lines. To compensate for the "non-intersecting" ends of the wire, take 20-30% longer than necessary for the treatment of the tumor. In a bulk implant, the sources in the cross section are located at the vertices of equilateral triangles or squares.

The dose to be delivered to the tumor is calculated manually using graphs, such as Oxford charts, or on a computer. First, the basic dose is calculated (the average value of the minimum doses of radiation sources). The therapeutic dose (eg, 65 Gy for 7 days) is selected based on the standard (85% of the basic dose).

The normalization point when calculating the prescribed radiation dose for surface and in some cases intracavitary brachytherapy is located at a distance of 0.5-1 cm from the applicator. However, intracavitary brachytherapy in patients with cancer of the cervix or endometrium has some features. Most often, the Manchester method is used in the treatment of these patients, according to which the normalization point is located 2 cm above the internal os of the uterus and 2 cm away from the uterine cavity (the so-called point A) . The calculated dose at this point makes it possible to judge the risk of radiation damage to the ureter, bladder, rectum and other pelvic organs.

Development prospects

To calculate the doses delivered to the tumor and partially absorbed by normal tissues and critical organs, complex methods of three-dimensional dosimetric planning based on the use of CT or MRI are increasingly used. To characterize the dose of irradiation, only physical concepts are used, while the biological effect of irradiation on various tissues is characterized by a biologically effective dose.

With fractionated administration of high-activity sources in patients with cancer of the cervix and uterine body, complications occur less frequently than with manual administration of low-activity radiation sources. Instead of continuous irradiation with low activity implants, one can resort to intermittent irradiation with high activity implants and thereby optimize the radiation dose distribution, making it more uniform throughout the irradiation volume.

Intraoperative radiotherapy

The most important problem of radiation therapy is to bring the highest possible dose of radiation to the tumor so as to avoid radiation damage to normal tissues. To solve this problem, a number of approaches have been developed, including intraoperative radiotherapy (IORT). It consists in the surgical excision of the tissues affected by the tumor and a single remote irradiation with orthovoltage x-rays or electron beams. Intraoperative radiation therapy is characterized by a low rate of complications.

However, it has a number of disadvantages:

• the need for additional equipment in the operating room;
• the need to comply with measures to protect medical personnel (because, unlike diagnostic X-ray examination the patient is irradiated in therapeutic doses);
• the need for the presence of an oncoradiologist in the operating room;
• radiobiological effect of a single high dose of radiation on normal tissues adjacent to the tumor.

Although the long-term effects of IORT are not well understood, animal studies suggest that the risk of adverse long-term effects a single exposure to a dose of up to 30 Gy is negligible if you protect normal tissues with high radiosensitivity (large nerve trunks, blood vessels, spinal cord, small intestine) from radiation exposure. The threshold dose of radiation damage to the nerves is 20-25 Gy, and the latent period clinical manifestations after irradiation ranges from 6 to 9 months.

Another danger to be considered is tumor induction. A number of studies in dogs have shown a high incidence of sarcomas after IORT compared with other types of radiotherapy. In addition, planning IORT is difficult because the radiologist does not have accurate information regarding the amount of tissue to be irradiated prior to surgery.

The use of intraoperative radiation therapy for selected tumors

Rectal cancer. May be useful for both primary and recurrent cancers.

Cancer of the stomach and esophagus. Doses up to 20 Gy appear to be safe.

bile duct cancer. Possibly justified with minimal residual disease, but impractical with an unresectable tumor.

Pancreas cancer. Despite the use of IORT positive influence its outcome of treatment has not been proven.

Tumors of the head and neck.

• According to individual IORT centers - safe method well tolerated and with promising results.
• IORT is warranted for minimal residual disease or recurrent tumor.

brain tumors. The results are unsatisfactory.

Conclusion

Intraoperative radiotherapy, its use limits the unresolved nature of some technical and logistical aspects. Further increase in the conformity of external beam radiation therapy eliminates the benefits of IORT. In addition, conformal radiotherapy is more reproducible and free from the shortcomings of IORT regarding dosimetric planning and fractionation. The use of IORT is still limited to a small number of specialized centers.

Open sources of radiation

Achievements nuclear medicine in oncology are used for the following purposes:

• clarification of the localization of the primary tumor;
• detection of metastases;
• monitoring the effectiveness of treatment and detection of tumor recurrence;
• targeted radiation therapy.

radioactive labels

Radiopharmaceuticals (RPs) consist of a ligand and an associated radionuclide that emits γ rays. The distribution of radiopharmaceuticals in oncological diseases may deviate from the normal. Such biochemical and physiological changes in tumors cannot be detected using CT or MRI. Scintigraphy is a method that allows you to track the distribution of radiopharmaceuticals in the body. Although it does not provide an opportunity to judge anatomical details, nevertheless, all these three methods complement each other.

Several radiopharmaceuticals are used in diagnostics and for therapeutic purposes. For example, iodine radionuclides are selectively taken up by active thyroid tissue. Other examples of radiopharmaceuticals are thallium and gallium. There is no ideal radionuclide for scintigraphy, but technetium has many advantages over others.

Scintigraphy

A γ-camera is usually used for scintigraphy. With a stationary γ-camera, plenary and whole-body images can be obtained within a few minutes.

Positron emission tomography

PET uses radionuclides that emit positrons. This is a quantitative method that allows you to get layered images of organs. The use of fluorodeoxyglucose labeled with 18 F makes it possible to judge the utilization of glucose, and with the help of water labeled with 15 O, it is possible to study cerebral blood flow. Positron emission tomography makes it possible to differentiate the primary tumor from metastases and evaluate tumor viability, tumor cell turnover, and metabolic changes in response to therapy.

Application in diagnostics and in the long-term period

Bone scintigraphy

Bone scintigraphy is usually performed 2-4 hours after injection of 550 MBq of 99Tc-labeled methylene diphosphonate (99Tc-medronate) or hydroxymethylene diphosphonate (99Tc-oxidronate). It allows you to get multiplanar images of bones and an image of the entire skeleton. In the absence of a reactive increase in osteoblastic activity, a bone tumor on scintigrams may look like a "cold" focus.

High sensitivity of bone scintigraphy (80-100%) in the diagnosis of metastases of breast cancer, prostate cancer, bronchogenic lung cancer, gastric cancer, osteogenic sarcoma, cervical cancer, Ewing's sarcoma, head and neck tumors, neuroblastoma and ovarian cancer. The sensitivity of this method is somewhat lower (approximately 75%) for melanoma, small cell lung cancer, lymphogranulomatosis, kidney cancer, rhabdomyosarcoma, multiple myeloma and bladder cancer.

Thyroid scintigraphy

Indications for thyroid scintigraphy in oncology are the following:

• study of a solitary or dominant node;
• control study in the long-term period after surgical resection of the thyroid gland for differentiated cancer.

Therapy with open sources of radiation

Targeted radiation therapy with radiopharmaceuticals, selectively absorbed by the tumor, has been around for about half a century. A rational pharmaceutical preparation used for targeted radiation therapy should have a high affinity for tumor tissue, a high focus/background ratio, and be retained in the tumor tissue for a long time. The radiation of the radiopharmaceutical must have a sufficiently high energy to provide therapeutic effect, but limited mainly to the boundaries of the tumor.

Treatment of differentiated thyroid cancer 131 I

This radionuclide makes it possible to destroy the tissue of the thyroid gland remaining after total thyroidectomy. It is also used to treat recurrent and metastatic cancer of this organ.

Treatment of tumors from neural crest derivatives 131 I-MIBG

Meta-iodobenzylguanidine labeled with 131 I (131 I-MIBG). successfully used in the treatment of tumors from derivatives of the neural crest. A week after the appointment of the radiopharmaceutical, you can perform a control scintigraphy. Treatment for pheochromocytoma positive result more than 50% of cases, with neuroblastoma - 35%. Treatment with 131 I-MIBG also gives some effect in patients with paraganglioma and medullary thyroid cancer.

Radiopharmaceuticals that selectively accumulate in bones

The frequency of bone metastases in patients with breast, lung, or prostate cancer can be as high as 85%. Radiopharmaceuticals that selectively accumulate in bones are similar in their pharmacokinetics to calcium or phosphate.

The use of radionuclides, selectively accumulating in the bones, to eliminate pain in them began with 32 P-orthophosphate, which, although it turned out to be effective, was not widely used due to its toxic effect on the bone marrow. 89 Sr was the first patented radionuclide authorized for systemic therapy bone metastases in prostate cancer. After intravenous administration 89 Sr in an amount equivalent to 150 MBq, it is selectively absorbed by the areas of the skeleton affected by metastases. This is due to reactive changes in the bone tissue surrounding the metastasis and an increase in its metabolic activity. Inhibition of bone marrow functions appears after about 6 weeks. After a single injection of 89 Sr in 75-80% of patients, the pain quickly subsides and the progression of metastases slows down. This effect lasts from 1 to 6 months.

Intracavitary therapy

The advantage of the direct introduction of the radiopharmaceutical into the pleural cavity, pericardial cavity, abdominal cavity, bladder, cerebrospinal fluid or cystic tumors, there is a direct effect of the radiopharmaceutical on the tumor tissue and the absence of systemic complications. Typically, colloids and monoclonal antibodies are used for this purpose.

Monoclonal antibodies

When monoclonal antibodies were first used 20 years ago, many began to consider them a miracle cure for cancer. The task was to obtain specific antibodies to active tumor cells that carry a radionuclide that destroys these cells. However, the development of radioimmunotherapy is currently more problematic than successful, and its future is uncertain.

Total body irradiation

To improve the results of treatment of tumors sensitive to chemo- or radiotherapy, and eradication of stem cells remaining in the bone marrow, before transplantation of donor stem cells, an increase in doses of chemotherapy drugs and high-dose radiation is used.

Targets for whole body irradiation

Destruction of the remaining tumor cells.

Destruction of residual bone marrow to allow engraftment of donor bone marrow or donor stem cells.

Providing immunosuppression (especially when the donor and recipient are HLA incompatible).

Indications for high dose therapy

Other tumors

These include neuroblastoma.

Types of bone marrow transplant

Autotransplantation - stem cells are transplanted from blood or cryopreserved bone marrow obtained before high-dose irradiation.

Allotransplantation - bone marrow compatible or incompatible (but with one identical haplotype) for HLA obtained from related or unrelated donors is transplanted (registries of bone marrow donors have been created to select unrelated donors).

Screening of patients

The disease must be in remission.

There must be no serious impairment of the kidneys, heart, liver, and lungs in order for the patient to cope with the toxic effects of chemotherapy and whole-body radiation.

If the patient is receiving drugs that can cause toxic effects similar to those of whole-body irradiation, the organs most susceptible to these effects should be specifically investigated:

• CNS - in the treatment of asparaginase;
• kidneys - in the treatment of platinum preparations or ifosfamide;
• lungs - in the treatment of methotrexate or bleomycin;
• heart - in the treatment of cyclophosphamide or anthracyclines.

If necessary, assign additional treatment for the prevention or correction of dysfunctions of organs that may be particularly affected by whole-body irradiation (for example, the central nervous system, testicles, mediastinal organs).

Training

An hour before exposure, the patient takes antiemetics, including serotonin reuptake blockers, and is given intravenous dexamethasone. For additional sedation, phenobarbital or diazepam can be given. In young children, if necessary, resort to general anesthesia with ketamine.

Methodology

The optimal energy level set on the linac is approximately 6 MB.

The patient lies on his back or on his side, or alternating position on his back and on his side under a screen made of organic glass (perspex), which provides skin irradiation with a full dose.

Irradiation is carried out from two opposite fields with the same duration in each position.

The table, together with the patient, is located at a distance greater than usual from the X-ray apparatus, so that the size of the irradiation field covers the entire body of the patient.

Dose distribution during whole body irradiation is uneven, which is due to the unequal irradiation in the anteroposterior and posteroanterior directions along the whole body, as well as the unequal density of organs (especially the lungs compared to other organs and tissues). Boluses or shielding of the lungs are used to more evenly distribute the dose, but the mode of irradiation described below at doses not exceeding the tolerance of normal tissues makes these measures redundant. The organ of greatest risk is the lungs.

Dose calculation

Dose distribution is measured using lithium fluoride crystal dosimeters. The dosimeter is applied to the skin in the area of ​​the apex and base of the lungs, mediastinum, abdomen and pelvis. The dose absorbed by tissues located in the midline is calculated as the average of the dosimetry results on the anterior and posterior surfaces of the body, or CT of the whole body is performed, and the computer calculates the dose absorbed by a particular organ or tissue.

Irradiation mode

adults. The optimal fractional doses are 13.2-14.4 Gy, depending on the prescribed dose at the normalization point. It is preferable to focus on the maximum tolerated dose for the lungs (14.4 Gy) and not exceed it, since the lungs are dose-limiting organs.

Children. Tolerance of children to radiation is somewhat higher than that of adults. According to the scheme recommended by the Medical Research Council (MRC), the total radiation dose is divided into 8 fractions of 1.8 Gy each with a treatment duration of 4 days. Other schemes of whole body irradiation are used, which also give satisfactory results.

Toxic manifestations

acute manifestations.

• Nausea and vomiting - usually appear approximately 6 hours after exposure to the first fractional dose.
• Swelling of the parotid salivary gland - develops in the first 24 days and then disappears on its own, although patients remain dry in the mouth for several months after that.
• Arterial hypotension.
• Fever controlled by glucocorticoids.
• Diarrhea - appears on the 5th day due to radiation gastroenteritis (mucositis).

Delayed toxicity.

• Pneumonitis, manifested by shortness of breath and characteristic changes on chest x-ray.
• Drowsiness due to transient demyelination. Appears at 6-8 weeks, accompanied by anorexia, in some cases also nausea, disappears within 7-10 days.

late toxicity.

• Cataract, the frequency of which does not exceed 20%. Typically, the incidence of this complication increases between 2 and 6 years after exposure, after which a plateau occurs.
• Hormonal changes leading to the development of azoospermia and amenorrhea, and subsequently - sterility. Very rarely, fertility is preserved and a normal pregnancy is possible without an increase in cases of congenital anomalies in the offspring.
• Hypothyroidism, which develops as a result of radiation damage to the thyroid gland, in combination with damage to the pituitary gland or without it.
• In children, growth hormone secretion may be impaired, which, combined with early closure of the epiphyseal growth zones associated with whole body irradiation, leads to growth arrest.
• Development of secondary tumors. The risk of this complication after irradiation of the whole body increases 5 times.
• Prolonged immunosuppression can lead to the development of malignant tumors of the lymphoid tissue.

Radiation therapy (radiotherapy) is the effect on the patient's body of ionizing radiation of elements that have pronounced radioactivity in order to treat oncological diseases. Many consciously choose this particular method of treatment, but it is worth remembering that radiation therapy not only destroys cancer cells, it also damages healthy tissues. The consequences of such exposure may appear immediately after the procedures or within six months after the end of treatment.

Indications

Radiation exposure is used as an independent method in the treatment of cancer:

• skin, lips;
• nasopharynx and oral cavity;
• tonsils;
• larynx;
• cervix (as the main method of treatment, radiation therapy is used only in the early stages of tumor development);
• at the initial stage of development of lymphoma, sarcoma.

For the treatment of other types of cancer, radiation therapy is used only in combination and cannot be used as an independent method. Also, radiation therapy is not used separately in the treatment of oncological diseases in children, but only as part of a comprehensive course of treatment.

Contraindications

• Cachexia (rapid weight loss).
• Anemia (if it is caused by the action of cancer on the hematopoietic system).
• Decreased levels of white blood cells, lymphocytes and platelets.
• Diseases with high fever.
• Myocardial infarction.
• Allergic dermatitis, various skin diseases, foci of purulent or non-purulent inflammation in the area through which the beam must pass.
• Kidney diseases.
• Pulmonary, cardiac or vascular insufficiency (during chest irradiation).
• Diseases of the central nervous system.
• active form of tuberculosis.
• Decompensated diabetes mellitus.
• Cancer that grows into nearby tissues, large vessels, hollow organs, complicated by bleeding and decay.
• Radiation sickness in a patient.
• Multiple metastases of the tumor formation.
• Cancer of the lung with cancerous pleurisy.

Kinds

Distinguish two different types radiotherapy, depending on what particles the tumor is irradiated with: corpuscular and photon. The first type of irradiation uses alpha and beta particles, as well as beams of neutrons, electrons and protons. Photon irradiation is carried out by exposure to gamma rays and x-rays. For example, electrons are used to destroy tumors located close to the skin, and protons are used for deep-seated tumors (proton therapy).

According to the method of influence, they distinguish:

• contact method. It is used quite rarely and only in cases where malignant neoplasms are on the surface. In this case, the radiation source is applied directly to the tumor. The main advantage of the contact method is that with it there is practically no effect on nearby tissues.
• remote method. This method is the most common, as it is universal. With remote exposure on the path of the radiation, there are healthy tissues and organs that suffer during irradiation. The more tissue between the source of radiation and the tumor, the greater the dose must be sent to destroy it, and, therefore, the more damage is done to healthy tissues.
• The interstitial (brachytherapy) method is based on the introduction of a radiation source into the tumor tissues in the form of needles, balls, capsules, etc. Solutions that are introduced into the body in one way or another are also used. Their action lies in the ability of individual tissues to accumulate certain radionuclides (for example, iodine accumulates in the thyroid gland).

There are also conformal, stereotaxic, adjuvant, intraoperative, interstitial radiation therapy.

How does it go

Treatment with radiation therapy is carried out in several stages, the first of which is called planning (pre-radiation). At this stage, several specialists at once (oncologist, radiotherapist, dosimetrist) calculate the correct radiation doses, choose the best way its introduction into tissues during brachytherapy (in this case, the brachytherapist is also connected), determine the allowable load and the reserve capacity of nearby tissues that may be exposed to radiation.

The second stage (beam period) consists in the irradiation itself according to the scheme developed earlier. The course of radiotherapy lasts up to 7 weeks, and in the preoperative period up to 3 weeks. Sessions are held 5 days a week, with a break of 2 days.

The procedure is carried out in a special isolated room. Doctors lay the patient on a table or chair, install a radiation source on the marked area, and cover other parts of the body with protective blocks that will protect the skin and body from radiation. A session of exposure to ionizing rays is painless and usually lasts from 1 to 5 minutes.

Effects

Complications of radiation techniques are manifested in different stages treatment of malignant tumors, including after the completion of procedures. Already from the first sessions, many patients complain of redness and dryness of the skin. A little later, peeling and cracks may begin in these areas. Skin pigmentation, burns are also possible.

The effects of radiation therapy depend on the location of the tumor.

When irradiating the pelvis, the following are observed:

• Vomiting and nausea.
• Violation of the intestines and bladder.
• Indigestion.
• In women - a violation of the functioning of the ovaries, and, consequently, a failure menstrual cycle or complete cessation of menstruation, dryness and itching in the vagina.
• During pregnancy, radiation therapy has a negative effect on the fetus, the results of such exposure cannot be predicted.
• In men, a decrease in the number of active spermatozoa.

For breast cancer:

• Cough.
• Dyspnea.
• Difficulty breathing and swallowing.
• Pain in the chest.
• Inflammation of the mucous membrane of the esophagus, which manifests itself in the form of pain when swallowing, heartburn, sensation of a lump in the throat.
• In women - swelling and compaction of the mammary glands.

For brain cancer:

• Hair loss.
• The appearance of small wounds on the scalp.
• High body temperature.
• Nausea, vomiting.
• Drowsiness.

With basalioma (malignant tumor of the skin):

• Swelling and peeling of the skin.
• Severe itching of the skin and burning.

For prostate cancer:

• Irritable bowel syndrome - constipation, diarrhea, bloating.
• Cystitis.
• Urinary incontinence.
• Erection problems that can lead to impotence.
• Narrowing of the urethra.

For cervical cancer:

• Redness and peeling of the skin.
• Loss of hair in the pubic area.
• Narrowing of the vagina.
• Dryness and burning in the genital area.

For acoustic neuroma:

• Nerve damage.
• Hearing loss.
• Facial paralysis.

Other possible consequences radiation treatment:

• Increased fatigue, weakness.
• Mental changes: depression, sleep disturbances, irritability, frequent mood swings, apathy, depression;
• Dizziness and headaches.
• Belching.
• Flatulence.
• weight loss.
• Increased salivation or dry mouth.
• Stomach ache.
• Constant thirst.
• Violation of hematopoiesis: a decrease in the level of leukocytes and erythrocytes in the blood, a decrease in hemoglobin.
• Decreased immunity.

Recovery after therapy

Rehabilitation begins immediately after the irradiation sessions and is as follows:

• Gentle mode.
• Ensuring proper sleep and rest.
• Rejection of bad habits.
• Frequent walks in the fresh air.
• Regular moderate exercise.
• Healthy food.
• Wearing loose clothing in natural fabrics.
• Taking vitamins.

After radiotherapy, it is forbidden to heat the irradiated area, put cold compresses on it, wash it with hot water, comb it, lubricate it with iodine and other alcohol tinctures. Recovery skin it is necessary to use the means recommended by the attending physician.

Also read about what antioxidants are, where they are found and how exactly they help to cope with the consequences of radiation and chemical therapy for oncological diseases.

Food

One of the side effects of radiotherapy is loss of appetite, but despite this, for a speedy recovery, it is necessary to eat enough food. Dietary nutrition in the treatment of radiation exposure involves the rejection of dairy products and foods that increase gas formation - legumes (beans, peas, etc.) and all types of cabbage. Also from the diet should be excluded:

• Whole grain cereals.
• Raw vegetables.
• Mushrooms.
• Spices.
• Marinades, smoked meats.

Useful for irradiation are:

• Berries.
• Greens.
• Walnuts.
• Fruits (bananas, apples).
• Crackers.

After radiation therapy, you can gradually include low-fat cheese, pumpkin, boiled lean fish, white meat (chicken or rabbit), vegetable soups and dairy products. You need to eat food often and in small portions.

In addition, during and after radiotherapy, you need to drink as much liquid as possible, prefer still water, green tea, non-acid compotes and diluted light juices.

Alpha, beta and gamma particles, X-ray and neutron radiation have found their indispensable application in modern oncology for the treatment of neoplasms, the termination of division and destruction of pathogenic and cancer cells, the destruction of the molecular structure and the further synthesis of their DNA.

Pre-planning for radiotherapy is a complex process.

It provides for an individual choice of the required dose of radiation, the duration and number of radiation therapy sessions, the search for ways to remove radiation from the body after exposure and prevent the appearance of more serious complications like radiation sickness.

Sources of radiation

The procedures that are carried out to diagnose the lesion and its further treatment are used. Radiography, MRI, contact, radionuclide and remote action of radiation are widely used.

Methods for conducting radiation therapy are diverse:

1. static. Targeted multiple or unilateral effects on tumor cells;
2. mobile. The radiation beam is moved, the maximum radioactive dose is used;
3. application. Applicators are placed on the skin. The procedure is recommended for benign and malignant tumors.
4. interior. Administration of radiation sources in the form of preparations for oral administration or through the blood
5. intracavitary. Appointment of special radioactive substances;
6. interstitial. Cobalt needles or threads containing iridium are injected under the patient's skin.

The course of radiation therapy lasts no more than 2-3 weeks. During this time, a person receives up to 200 rads for one exposure, and 5000 rads for the entire period of treatment. Additionally, steroids and are prescribed.

It is forbidden to take vitamins and antioxidants, because the presence of antioxidants in them neutralizing the action of free radicals removes radiation from the body.

The effect of radiation on the body

Effective treatment radiation, unfortunately, harms healthy tissues and organs. And each new dose of radiation that a person receives during radiation therapy lowers the protective functions of the body and weakens the immune system.

What is dangerous radiation and what happens after exposure:

• skin damage. Accompanied by pain, swelling, redness, bubbles form, pigmentation appears, hair stops growing. Radiation ulcers are a complication. May cause skin cancer
• violation of the mucous membranes of the larynx, oral cavity and respiratory organs. The structure of the lung tissue becomes heterogeneous, a complication is acute radiation pneumonia, foci of infiltration. Hyperemia, erosion and necrosis of individual areas. Radiation therapy of the larynx provokes a cough with sputum, a violation of the secretion of saliva;
• changes in bowel function. Necrosis and ulcerative processes are observed on the walls, unstable stools, diarrhea, and cases of bleeding from the intestines are not uncommon. Fistulas, scars are formed, the absorption of vitamin B 12, proteins and iron is disturbed;
• partial dysfunction of the urinary system. kidney failure, nephritis, increased blood urea. From the side of the bladder, radiation cystitis, ulcers, necrosis and fistulas are possible;
• liver problems. Radiation hepatitis, fibrosis;
• consequences for the spinal cord are numbness of the limbs, irritability and weakness, pain in the sacrum, dizziness;
• brain complications. Memory impairment, emotional instability.

It can provoke ionizing radiation and radiation sickness, which leads to a reduction in the patient's life expectancy, functional disorders of the circulatory, endocrine and respiratory systems.

There are changes of a dystrophic nature, malignant neoplasms and hereditary genetic mutations, sexual impotence are possible.

Medical treatment after irradiation

intensive treatment cancer and tumors should be combined. In addition to radiation therapy, the oncologist must teach the patient how to safely remove radiation from the body for health, which pills and drugs are better to take after radiation:

1. "Potassium iodide". Prevents the accumulation of large amounts of iodine and reduces its absorption thyroid gland, provides protection of the endocrine system from radiation. The daily intake is from 100 to 250 mg;
2. "Revalid". Combined drug, compensates for the lack of important vitamins, micro and macro elements after radiation therapy, normalizes protein and fat metabolism, reduces intoxication of the body, strengthens the immune system;
3. "Methandrostenolone". It is prescribed for severe exhaustion of the body. A steroid that activates the regeneration of cells, tissues and muscles, promotes the synthesis of DNA and RNA, prevents oxygen starvation organism. The maximum daily dose is 50 mg;
4. "Mexamine". The use of a serotonin receptor stimulator 50-100 mg before a session for 30-40 minutes increases intestinal motility, prevents the absorption of harmful toxic substances;
5. "Nerobol". It is recommended for violation of protein metabolism, weakening of the body, weight loss and muscular dystrophy. The norm of the drug per day - 5 mg twice;
6. "Amygdalin" or vitamin B17. It affects cancer cells, poisons and inhibits their growth, nourishes healthy tissues. In addition, it has an antiseptic and analgesic effect. The dosage is prescribed only by a specialist.

Without exception, all drugs are potent and have a large number of side effects. It is possible to carry out their reception only after consultation and appointment by an oncologist.

Products for removing radiation from the body

It is very important to get proper nutrition after radiation exposure. It should saturate the body with the missing beneficial substances, be energetically valuable, restore the immune system.

It is also necessary to include in the diet foods and drinks that remove radiation from the body:

• fermented milk products, goat's milk, butter and low-fat cottage cheese;
• quail eggs. Remove radionuclides, strengthen the tone and immune system;
• pectin. Cleanses the body of toxins, preserves the intestinal microflora. They are rich in jelly, carrots, beets, peaches, strawberries, pears, plums;
• cellulose. Regulates metabolic processes, removes toxins, prevents the increase of sugar and bad cholesterol. Pasta, raw vegetables, herbs, cilantro, red beets. Fruits with fiber - grapefruit, grapes, blackberries, plums;
• green tea. Tones, relieves spasms of cerebral vessels, has anti-inflammatory, antibacterial and analgesic effects. Frees from carcinogens and free radicals;
• selenium. Stimulates the production of leukocytes and erythrocytes, neutralizes free radicals that can destroy cells. Prevents cell mutation, prevents tumor formation, participates in the production of hormones. Wheat, lentils, liver, eggs, rice, octopus;
• potassium. Saturates tissues with oxygen, accelerates metabolism. Wheat bran, dried apricots, yogurt, sardine, tuna, rabbit meat;
• vitamin R. Strengthens blood vessels and small capillaries, normalizes the work of the heart and arterial pressure. Contained in garlic, tomatoes, blackcurrant;
• vitamin A. Persimmon, celery, parsley, carrots, rose hips;
• vitamins of group B. Reduce the growth of tumor cells, prevent metastases. They increase the body's resistance, maintain the normal condition of the skin, mucous membranes and intestinal microflora, are responsible for vision and memory, participate in intracellular metabolism, maintain muscle tone, stimulate the heart, liver and kidneys. Are situated in in large numbers in flaxseeds, poultry, liver, cereals, nuts, asparagus, egg yolk;
• vitamin C. It is used in the prevention of cancer, during the treatment of tumor diseases. Promotes the removal of heavy metals and toxins. Seaweed, currant, sorrel, spinach, cabbage;
• vitamin E. Prevents aging, strengthens the immune system, cleanses blood vessels from blockage. Olive, sunflower, wheat germ oil, banana.

It is necessary to combine nutrition in the treatment of the consequences of radiation with the intake activated carbon. He is potent safe sorbent. Half an hour before meals, grind the tablets, check the dosage with the doctor, drink the resulting powder with plenty of water.

What foods remove radiation better, how to make up a diet, it is better to check with the oncology center.

What Not to Eat and Drink After Radiation Therapy

Along with useful vitamins and dietary supplements that cleanse the body of toxins and metals, there are absolutely useless ones.

During the period of exposure and after it, doctors inform patients which products do not remove radiation and are prohibited:

1. beef;
2. coffee;
3. sugar;
4. yeast dough;
5. alcohol;
6. legumes;
7. raw vegetables;
8. whole grain products;
9. cabbage.

The properties that products possess, as in the above list, do not allow radiation to be removed from the body. Detain radioactive elements, impede the work of the gastrointestinal tract, disrupt blood circulation, and negatively affect the central nervous system.

During the passage of radiation therapy and during the rehabilitation period, they must be avoided.

Folk remedies for radiation

Self-medication during exposure is strictly prohibited. Vitamins A, C and E, which are found in many medicinal plants, can reduce the level of radiation needed in radiotherapy. After completing the course, excretion folk remedies radiation from the body is allowed.

Modern herbal medicine for oncology uses the following herbs:

• tincture that helps after radiation. Ingredients: peppermint, chamomile, plantain leaves 50 grams each, 25 grams each yarrow and St. John's wort. Mix dry plants, brew a tablespoon in 500 grams of boiling water. Leave for 1 hour. Take ½ cup 4 times a day before meals;
• black radish. To prepare the tincture, you will need 1 kg of washed vegetables and a liter of vodka. Insist in a dark place for 15 days. After straining, drink ¼ cup three times a day half an hour before meals
• nettle leaves. Dry plant - 5 tablespoons, 2 cups boiling water. Leave to brew for 1 hour. Pass through gauze. Drink a decoction of 200 ml 3 times for no more than a month with a break of two weeks;
• celery juice. Natural honey - 1 teaspoon and freshly squeezed spicy plant- 50 ml. Mix. It must be consumed in the morning one hour before the intended meal;
• rose hip. Fruits - 40 grams, boiling water - 1 liter. Leave to infuse in a thermos for 2-3 hours. Drink the finished infusion in one day.

So that phytotherapeutic methods do not cause irreparable harm to health, you should contact specialized rooms with professional therapists. Properly selected collections and compositions of herbs will help get rid of the effects of radiation exposure and restore the body.

Radiation Protection Methods

After a course of radiation therapy and recovery, experts recommend avoiding any possible source of radiation.

1. wear clothes only from natural fabrics;
2. eliminate bad habits;
3. limit exposure to direct ultraviolet rays;
4. take pills and drugs that protect against radiation. Eleutherococcus extract, Iodomarin 100, Ammifurin, Sodecor, Magnesium sulfate.

It is better to coordinate all your subsequent actions after oncological diseases with a specialist.

Self-prescribing and taking medications can provoke serious consequences for a still weak body and slow down the healing process.

There can be no identical scheme of radiation therapy. It differs from patient to patient and depends on many factors. So, depending on the type of cancer, there are different radiation plans. The radiation therapy regimen is also affected by the state of the body, the age of the patient, the experience of radiation in the past, the size and location of the tumor.

Only with so-called radiosurgical interventions is a single irradiation performed. Otherwise, the radiooncologist almost always gives the required dose of radiation not at once, but divides it into several sessions. This is because healthy cells recover from the damaging effects of radiation better and faster than cancer cells. Fractionated irradiation, as it is called in medical parlance, thus gives healthy cells time to recover before the next session. This reduces the side effects and effects of radiation therapy.

How long does a course of radiation therapy take?

With conventional fractionated radiotherapy, the patient is irradiated from Monday to Friday, respectively, once a day - for five to eight weeks. Weekends are free. If two or three exposures are performed during the day, radiologists speak of hyperfractionation. It may be useful for some tumors. On the contrary, with other types of cancer, a smaller number of sessions per week is sufficient. In these cases, we speak of hypofractionation.

In order for the radiooncologist to always accurately hit the radiation area during individual sessions, the doctor makes marks on the patient's skin with a special paint. It is important not to wash off these marks until the radiation therapy is over.

How long does radiation therapy last for individual treatment sessions?

In most cases, radiation therapy is performed on an outpatient basis. As a rule, the session lasts from 15 to 45 minutes. Most of this time is occupied by the correct laying and installation of the device for irradiation, because it is necessary to recreate the previous position of the patient with the utmost accuracy. That is why the doctor asks not to wash off the marker marks on the skin. Sometimes small tattoos are applied in these places, the absolute accuracy of the irradiation is so important. The irradiation itself lasts only a few minutes (from one to five). During the session, medical personnel must leave the treatment room, this is prescribed by the instructions for radiation protection. However, the patient has eye contact with the doctor through the window and can usually also talk to him through the intercom.

How is radiation therapy performed?

The doctor draws up a plan of radiation therapy in detail, calculates the course (total) radiation dose and per session, determines the number of sessions, their duration, and the break between them. Usually the patient gets acquainted with this scheme and asks questions that concern him.

Councils for the passage of radiation therapy.

1. Clothing should be loose, with an open collar, not restrict movement. Sometimes the patient is offered a disposable hospital gown.
2. The patient can be fixed during the procedure using special devices (masks, belts, mattresses, fasteners). This is necessary so that he does not move. Fixing devices do not cause discomfort.
3. Healthy organs and tissues are protected by special screens (blocks)
4. Sometimes a control picture is taken before the procedure in order to make sure that the patient is in the correct position.
5. Remember that the first session usually lasts longer than subsequent ones.
6. Do not dry your hair with a hair dryer during radiation therapy.
7. When leaving the house, it is necessary to protect the irradiated places from the sun, but you should not apply sunscreen. Wear a wide-brimmed hat, long sleeves, gloves, and sunglasses.
8. During irradiation, physical activity is contraindicated.
9. At the time of treatment, try to go outside during the period when the sun has already set.
10. Drink more fluids.

How is radiation therapy done?

The patient is placed on a special transforming table that can move. It is very important not to move during the radiation therapy session. Even the smallest changes in body position can cause the beams to no longer optimally reach the tumor and instead damage surrounding healthy tissue. This is especially critical, for example, in radiation therapy of a brain tumor.

However, for many people, lying completely still is not possible even for a couple of minutes. For this reason, doctors sometimes immobilize a patient or an area of ​​the body that will be exposed to radiation. Although often unpleasant, it protects healthy organs and greatly contributes to the success of the treatment. From the side of the irradiation itself, the patient does not feel anything during the therapy session. After the last session, the doctor once again examines his patient and conducts a detailed final conversation with him. This includes, for example, skin care, necessary follow-up examinations, nutrition after radiation therapy and recommendations for restoring and correcting your future lifestyle.

Cancer is the worst prognosis a doctor can offer. There is still no cure for this disease. The insidiousness of cancer is that it affects almost all known organs. In addition, cancer can launch its "tentacles" even in the body of pets. Is there a way to fight this enemy? One of the most effective methods is radiation therapy in oncology. But the bottom line is that many refuse such a prospect.

Let's go through the basics

What do we know about cancer? This disease is almost incurable. Moreover, the incidence is increasing every year. Most often, the French get sick, which is explained by the aging of the population, since the disease often affects people of age.

In fact, cancer is a disease of cells, during which they begin to continuously divide, forming new pathologies. By the way, cancer cells do not die, but only transform into a new stage. This is the most dangerous moment. In our body, a priori, there is a certain supply of cancer cells, but they can grow quantitatively due to external factors, which are bad habits, the abuse of fatty foods, stress, or even heredity.

At the same time, the tumor that is formed by these cells can be benign if it grows outside the organ. In such a situation, it can be cut out and thereby eliminate the problem. But if the tumor grows on the bone or it has grown through healthy tissues, then it is almost impossible to cut it out. In any case, if the tumor is removed surgically, radiation therapy is inevitable. In oncology, this method is quite common. But more and more sick people refuse this practice because of the fear of exposure.

Types of treatment

If there is a disease, then it is worth considering the main methods of treatment. These include surgical removal of the tumor. By the way, it is always removed with a margin to eliminate the risk of a possible germination of the tumor inside healthy tissues. In particular, in breast cancer, the entire gland is removed along with the axillary and subclavian lymph nodes. If you miss a certain part of the cancer cells, then the growth of metastases is accelerated and chemotherapy is required, which is effective method against rapidly dividing cells. Also in use is radiotherapy, which kills malignant cells. In addition, cryo- and photodynamic therapy, immunotherapy assisting immune system in the fight against cancer. If the tumor is found at an advanced stage, then combined treatment or the use of drugs that alleviate pain and depression may be prescribed.

Indications

So, when is radiation therapy needed in oncology? When talking with a sick person, the most important thing is to rationally explain the need for such a method of treatment and clearly formulate the task that you want to achieve in this way. If the tumor is malignant, then radiation therapy in oncology is used as the main method of treatment or in combination with surgery. The doctor expects the treatment to reduce the size of the tumor, temporarily stop growth, and alleviate the pain syndrome. For two-thirds of cancer cases, radiation therapy is used in oncology. The consequences of this method are expressed in increasing the sensitivity of the diseased area. For some types of tumors, radiation therapy is preferred over surgical method, as it is characterized by less trauma and the best cosmetic result in open areas.

For epithelial tumors, combined radiation and surgical treatment is indicated, with radiation being the first priority, since it helps to reduce the tumor and suppress its growth. If the operation was not effective enough, then postoperative irradiation is indicated.

In forms with distant metastases, a combination of radiation and chemotherapy is indicated.

Contraindications

When is radiation therapy clearly out of place in oncology? The consequences are not the most pleasant if there is lymphopenia, leukopenia, thrombocytopenia, anemia, as well as any diseases accompanied by high temperature and feverish condition. If chest irradiation is to be performed, the risk factor will be cardiovascular or respiratory failure as well as pneumonia.

Radiation therapy in oncology after surgery is indicated for those people who are distinguished by the health of the central nervous system and the genitourinary system. They must not endure acute diseases, have pustules, allergic rashes or inflammation on the skin. There are also conditions, for example, anemia cannot be considered as a contraindication if the bleeding comes from a tumor. Indeed, after the first sessions of therapy, bleeding may stop.

Unexpected Risk

Radiation therapy in oncology after surgery may be an unjustified risk if the patient's history contains a record of the tuberculous process. The fact is that irradiation makes it possible to exacerbate a dormant infection from latent foci. But at the same time, closed forms of tuberculosis will not be considered a contraindication, although they will require drug treatment during radiation therapy.

Accordingly, an aggravation will be possible subject to the existing inflammatory process, purulent foci, bacterial or viral infections.

Based on the foregoing, it can be revealed that the use of radiation therapy is determined by specific circumstances by a combination of arguments. In particular, the criteria will be the expected timing of the manifestation of results and the probable life expectancy of the patient.

Specific goals

Tumor tissue is very sensitive to radiation exposure. That is why radiation therapy has become widespread. Radiation therapy is used to treat oncology with the aim of damaging cancer cells and their subsequent death. The impact is carried out both on the primary tumor and on isolated metastases. Also, the goal may be to limit the aggressive growth of cells with the possible transfer of the tumor to an operable state. Also, to prevent the occurrence of metastases in cells, radiation therapy in oncology can be recommended. The consequences, reviews and attitudes of sick people differ polarly, since, in fact, it means irradiation of the body in order to destroy damaged cells. How will this affect health? Unfortunately, it is impossible to predict with accuracy, since everything depends on individual features organism.

Varieties of therapy

With an eye to the properties and sources of the ray beam, different kinds radiotherapy in oncology. These are alpha, beta, gamma therapies, as well as neutron, pi-meson and proton. There is also X-ray and electronic therapy. For each type of cancer, radiation exposure has a unique effect, as cells behave differently depending on the degree of damage and the severity of the disease. With equal success, you can count on a complete cure or an absolutely zero result.

When choosing a method of irradiation, the location of the tumor plays an important role, since it can be located near vital organs or blood vessels. Internal exposure is produced when a radioactive substance is placed into the body through the alimentary tract, bronchi, bladder or vagina. Also, the substance can be injected into the vessels or contact during surgery.

But external radiation goes through the skin. It can be general or focused on a specific area. The source of exposure may be radioactive chemicals or special medical equipment. If external and internal irradiation is performed simultaneously, then it is called combined radiotherapy. By the distance between the skin and the beam source, remote, close-focus and contact irradiation is distinguished.

Action algorithm

But how is radiation therapy done in oncology? Treatment starts with histological confirmation the presence of a tumor. Already on the basis of this document, the tissue affiliation, localization and clinical stage are established. The radiologist, based on these data, calculates the radiation dose and the number of sessions required for treatment. All calculations can now be done automatically, as there are appropriate computer programs. The available data also help determine whether radiotherapy should be given in combination with or without other modalities. If the treatment is combined, then irradiation can be carried out both before and after the operation. According to the standard, the duration of the course of radiation before surgery should be no more than three weeks. During this time, radiation therapy can significantly reduce the size of the tumor. In oncology, reviews of this method are very polar, since the effect remains unpredictable. It also happens that the body literally repels radiation or accepts it with healthy cells, and not sick ones.

If radiation therapy is performed after surgery, then it can last from a month to two.

Side effects of the procedure

After the start of the course of treatment, a sick person may experience weakness, chronic fatigue. His appetite decreases, his mood worsens. Accordingly, he can lose a lot of weight. Changes can be observed by tests - the number of erythrocytes, platelets and leukocytes decreases in the blood. In some cases, the place of contact with the beam beam may swell and become inflamed. Because of this, ulcers can form.

Until recently, irradiation was carried out without taking into account the fact that healthy cells could also get into the area of ​​action. However, science is moving forward and intraoperative radiation therapy has appeared in breast oncology. The essence of the technique is that the irradiation process can be started at the stage of the operation, that is, after excision, direct the beam to the site of intervention. Efficiency in this matter allows minimizing the likelihood of a residual tumor, since it is rendered harmless.

With a breast tumor, a woman always has a risk that she will have to part with her breast. This prospect is often even more frightening than a fatal disease. And breast reconstruction through intervention plastic surgeons too expensive for average residents. Therefore, women turn to radiation therapy as a salvation, since it can allow them to limit themselves to excision of the tumor itself, and not to remove the gland completely. Places of possible germination will be treated with rays.

The effect of radiation therapy directly depends on the health of the patient, his mood, existing side diseases and the depth of penetration of radiological rays. Often the effects of radiation appear in those patients who have undergone a long course of treatment. Minor pains can appear for a long time - it is the affected muscle tissue that reminds of itself.

The main problem of women

According to statistics, radiation therapy in uterine cancer is the most common method of treatment. This pathology occurs in older women. I must say that the uterus is a multi-layered organ, and cancer affects the walls, spreading to other organs and tissues. In recent years, uterine cancer has also been found among young women, which doctors often attribute to the early onset of sexual activity and carelessness in relation to protection. If you "catch" the disease on early stage, then it can be cured completely, but in the late period it will not be possible to achieve complete remission, but by following the recommendations of an oncologist, you can extend a person’s life.

Treatment for uterine cancer is based on surgical intervention, radiotherapy and chemotherapy. The bonus is hormonal treatment, special diet and immunotherapy. If the cancer is actively progressing, then excision is not the right way. Better results can be achieved with irradiation. The procedure is prohibited for anemia, radiation sickness, multiple metastases and other ailments.

Radiotherapy techniques in this case may differ in the distance between the source and the impact zone. Contact radiotherapy is the mildest, as it involves internal exposure: the catheter is inserted into the vagina. Healthy tissues are practically not affected. Can the transferred oncology be harmless in this case? After radiation therapy, after removal of the uterus and other unpleasant procedures, a woman is weak and vulnerable, so she absolutely needs to reconsider her lifestyle and diet.

The uterus is removed if the tumor has grown strongly and affected the entire organ. Alas, in this situation, the possibility of further procreation is called into question. But this is not the time to regret, since such drastic measures will extend the life of a sick woman. Now you need to reduce intoxication, which is carried out by drinking plenty of water, eating plant foods and vitamin complexes with the lion's share of antioxidants. Protein foods should be introduced into the diet gradually, focusing on fish, chicken or rabbit meat. Bad habits should be eliminated once and for all, and preventive visits to the oncologist should be introduced as a rule.

It is worth including foods that have anti-cancer effects in the diet. These include potatoes, cabbage in all varieties, onions, herbs and various spices. You can focus on dishes from cereals or whole grains. Soy, asparagus and peas are held in high esteem. Also useful are beans, beets, carrots and fresh fruits. It is still better to replace meat with fish and eat low-fat sour-milk products more often. But all alcoholic drinks, strong tea, smoked meats and salinity, marinades fall under the ban. We'll have to say goodbye to chocolate, convenience foods and fast food.