What is proton therapy?

Proton therapy is prescribed not only for malignant tumors, but also for benign tumors:

• primary head and neck tumors, which include tumors of different morphological types (chondromas, brain stem tumors, cancer of the larynx, trachea, nasopharynx, etc.);
• recurrent neoplasms (metastases) in the head and neck region after treatment (surgery, radiation and chemotherapy);
• tumors of the central nervous system;
• benign tumors of spinal canals;
• neoplasms with complex geometric structure and located in close proximity to critical structures (brainstem, optic nerves, etc.).

Proton therapy is an advanced treatment method in oncology. Due to its radical differences from linear radiotherapy in the principle of operation, proton therapy allows for a more gentle and organ-preserving treatment. Proton therapy is one of the most promising areas in the treatment of malignant neoplasms, as far as conservative methods are concerned. Many severe diseases, which were previously considered incurable, are now successfully treated, and the patient either goes into long-term remission or completely recovers.

• Proton therapy allows effective treatment of various types of cancer of complex localizations, where surgery or other methods are ineffective or cannot be used according to indications.
• It is one of the most precise treatment methods in oncology in terms of its effect on tumor cells.
• Proton therapy makes it possible to treat cancer localized near vital areas.
• Proton therapy is one of the least toxic methods of cancer treatment. The effects of the proton on healthy tissues may be localized, acute conditions are usually not present. After the procedure, the patient may experience tissue swelling, redness and skin irritation at the site of exposure.

Proton therapy, like any other types of cancer treatment, is a serious procedure that requires thorough preparation. In addition to the standard set of diagnostic tests, a specialized study, the so-called pre-radiation preparation, is done and a dosimetric treatment plan is drawn up. In order to avoid damage to healthy tissues and reduce the intensity of side effects, it is necessary to determine the exact location of the tumor – the target and risk contours. For this purpose, either MRI with contrast or PET/CT is performed, depending on the type of malignancy. Also, it is necessary to consult such specialists as an oncologist, neurosurgeon, chemotherapist, etc., based on the specifics of the course of the disease, and visit a multidisciplinary medical council.

Proton therapy – is a non-trivial and revolutionary method of cancer treatment. The achievement of scientists in the development of proton therapy is the destruction of atypical cells with minimal radiation exposure to the surrounding normal tissues. Protons are distinguished by their ability to produce maximum energy release at the moment of stopping, so if the peak of proton motion is correlated with the tumor, it is the tumor that will receive the greatest impact, not healthy tissues. This is a tremendous achievement of modern radiation therapy and oncology. Proton therapy allows obtaining a persistent effect, the so-called local control, within 90% of cases, but it is prescribed strictly in certain indications.

The 1st stage – fixation of the patient in the chair.
The patient’s chair rotates 360 degrees, which allows to direct the beam of charged particles to the epicenter of the tumor as accurately as possible. The patient must be completely immobile during the session. For patients undergoing treatment for head and neck cancer, special masks are individually made to fix the head in one position.

Stage 2 – checking coordinates and setting the chair in the correct position.
Using the built-in CT scanner, the patient’s position in the chair is corrected to achieve an irradiation accuracy of 0.3 millimeters.

The 3rd stage is the verification of the patient’s position with the preliminary calculations.
The irradiation process is simulated in accordance with the developed plan – the tomograph produces several images for comparison with the initial images approved during the planning of the procedure. If the slightest deviations are detected, the coordinates are corrected.

The duration of the session is up to 30 minutes – on average it is 10 minutes. The time frame is determined by the size of the irradiated target. The course of proton therapy can be quite long, it depends on many factors – the morphology and volume of the tumor, as well as the course of treatment (primary, postoperative or independent). The number of sessions prescribed varies from 5 to 35. Like linear radiation therapy, proton therapy does not cause any discomfort during the session. However, some complications may occur afterwards.

Proton therapy, like any other methods of cancer treatment, has side effects, but they are less pronounced than with traditional radiation therapy (and, even more so, chemotherapy). The intensity of the manifestation of complications depends largely on the localization of the tumor, as well as the current state of the patient’s health.

Complications caused by proton therapy can be generalized into two main groups:

• side effects of proton therapy itself:
  • tissue edema;
  • redness and irritation of the skin at the site of irradiation;
  • hair loss at the site of irradiation;
  • distortion of sensitivity, numbness of the skin.
• complications caused by destruction of tumor cells:
  • general weakness and rapid fatigue;
  • high body temperature;
  • various manifestations of allergies.

To relieve undesirable symptoms, supportive therapy is prescribed. In most cases, the manifestation of side effects stops after completion of the course of treatment.

The proton and photon therapy department at A.Tsyb Medical Radiological research Centre – branch of the National Medical Research Radiological Centre of the Ministry of Health of the Russian Federation, is equipped with a Russian-made proton accelerator Prometheus. This is a unique development that is invaluable for oncology. It was developed specifically for medical purposes under the supervision of Vladimir Egorovich Balakin, General Director of Lebedev Physical-Technical Center of the Russian Academy of Sciences, Corresponding Member of the Russian Academy of Sciences.