Proton therapy in the treatment of oncology

Proton therapy is a special type of radiation therapy. Protons are the source of ionizing radiation. Proton radiation destroys DNA in cancer cells and stops tumor growth. Proton beam therapy is an effective treatment for various types of cancer and some benign tumors. Proton therapy is considered the most precise and safe method of radiotherapy, so it is often used to treat cancer in children. Proton therapy is used both as an independent method of treating tumors, and as one of the types of treatment for combined therapy of oncological diseases (it can be prescribed after surgery, simultaneously with chemotherapy).

Conventional radiotherapy uses gamma or X-rays, which are produced in linear accelerators using photons and electrons. With such irradiation, energy begins to be released immediately after the penetration of photon radiation into the human body. Therefore, healthy tissues and organs are irradiated through which photon rays pass. This leads to the development of unpleasant side effects during and after radiation treatment, as well as after a certain period after a course of radiotherapy. Sometimes so serious that they require separate treatment.

Proton radiation is produced in special linear accelerators – synchrophasotrons (cyclotrons). Protons, unlike photons, release energy almost simultaneously, at a certain depth (at the location of the tumor). This feature is called the Bragg Peak. Due to this physical phenomenon, healthy tissues in the path of the proton beam are irradiated much less. Scientists have found that with proton therapy, the radiation dose in the tumor area is 30% more, and in the area of healthy tissues, the destructive effect of rays is 60% less than with traditional (photon) radiation therapy. Such data are published by the American Association of Clinical Oncologists, American Society of Clinical Oncology (ASCO).

Therefore, patients tolerate proton cancer treatment well. They maintain daily activity and a good quality of life. If unwanted symptoms appear, then for a short period of time, and they are reversible.

Oncologists take into account the main advantage of proton therapy – a sparing effect on the body when irradiating a cancerous pathological focus with maximum doses. Especially in cases where tumors are located with vital structures and organs that are sensitive to radiation. These include:

• brain and spinal cord;
• red bone marrow;
• lungs and heart;
• stomach and intestines;
• sexual glands.

Therefore, doctors recommend proton therapy:

• for the treatment of cancer in children;
• in the treatment of elderly and debilitated people who do not tolerate conventional radiation treatment;
• when repeat radiotherapy is needed for cancer recurrence;
• in cases of ineffectiveness of conventional radiotherapy;
• when it is necessary to simultaneously carry out high-dose chemotherapy and radiotherapy;
• when it is possible to cure cancer only with the help of proton therapy.

Proton beam therapy can be used for many types of cancer in adults and children.

A growing child’s body is very sensitive to ionizing radiation. In addition to adverse reactions during therapy, children may develop secondary radiation-induced cancer 5 to 20 years after treatment. Scientific studies have shown that with proton radiotherapy, the risk of developing such cancer is 4-10 times lower than with photon beam therapy. Therefore, for certain tumors and oncological diseases, pediatric oncologists recommend that proton therapy be given.

In pediatric oncological practice, proton therapy is used for the following neoplasms:

• brain tumors including glioblastoma, glioma, astrocytoma, meningioma, medulloblastoma;
• cancer of the optic nerve and retina;
• nasopharyngeal carcinoma;
• neuroblastoma;
• sarcomas of all kinds, including Ewing’s sarcoma;
• rare tumors, such as teratomas.

Children tolerate proton therapy well. Sometimes it replaces surgical treatment.

In the treatment of oncological diseases in adults, the range of indications for proton therapy is quite wide and includes:

• various tumors of the brain and base of the skull;
• malignant neoplasms of the head and neck, including the nasal cavity, paranasal sinuses, larynx;
• cancer of the eye and orbit (melanoma, retinoblastoma);
• tumors of the spinal cord and spine;
• cancer of the lung and bronchi, esophagus, breast;
• various sarcomas of any localization;
• inoperable hepatocellular cancer;
• prostate cancer.

The list of tumors that can be treated with proton radiation is constantly expanding. And there are cancers for which proton therapy is vital.

Recent guidelines for proton radiation treatment, including those of the American Radiation Society of Oncologists (ASTRO), recommend this type of radiotherapy for cancer:

• visual structures;
• base of the skull;
• spinal cord;
• hepatocellular cancer;
• all children with oncopathologies;
• patients who are prescribed a course of radiotherapy for cancer recurrence.

Proton therapy is especially indicated for chordomas and chondrosarcomas of the skull base. They cannot be removed surgically due to their proximity to the brain stem and it is dangerous to irradiate with a photon beam. Proton beam therapy provides an antitumor effect while preserving vital centers in the brain stem. Only after proton therapy can the eye and vision be saved in retinal melanoma.

Proton therapy is about the same as conventional radiotherapy.

With the help of proton beams, doctors perform:

• radiosurgery – 1-3 sessions of irradiation with a large dose;
• fractional radiotherapy – daily irradiation in small doses for several weeks (20-30 sessions).

Both options use an innovative radiation technology called pencil beam scanning (PBS). This technique ensures the repetition and accuracy of irradiation of a tumor of any shape throughout its entire thickness in just 1-3 minutes. A thin beam of protons “scans” a cancerous tumor with “pixel” millimeter precision.

Before starting treatment, doctors conduct a thorough 3D therapy planning based on CT and MRI data. Masks and other devices are used to ensure the correct position and immobility of the patient during the radiation session. Young children may require general anesthesia or sedation. The entire session lasts 30-45 minutes. Most of the time is spent preparing the patient (positioning) and setting up the device. Cancer treatment with protons does not require hospitalization. Proton therapy is carried out in treatment rooms in comfortable conditions for the patient.

Many patients who receive proton therapy have no adverse reactions. Some people may be concerned about general weakness and lack of appetite, redness and irritation of the skin in the area of radiation, which quickly disappear after discontinuation of therapy or with the use of symptomatic agents.

With all the advantages of proton therapy, there are also disadvantages:

• this is an expensive treatment: the average cost of a course of treatment is $40,000-50,000;
• not all types and stages of cancer can be treated with proton therapy (proton beams do not treat cancer of the skin, stomach, intestines, kidneys, bladder, genital organs, and a number of other tumors, as well as cancer with multiple metastases);
• not all countries can receive such therapy;
• not everywhere proton therapy is available to foreign patients;
• not all proton therapy centers treat a particular type of cancer.

Therefore, proton therapy is not always and not suitable for all patients. The price of photon radiosurgery on CyberKnife or GammaKnife devices, or intensity modulated radiotherapy (IMRT) is much less. And the efficiency and high-precision of such treatment on the devices of the latest generation are not inferior to proton therapy.

Proton beam therapy can only be carried out in specialized centers that are not related to conventional radiotherapy. This is a separate building with a 90-ton cyclotron and sophisticated devices for delivering radiation to the tumor. These centers employ highly specialized staff.

Proton therapy centers treat both adults and children. The specialists of the centers carefully select patients for cancer treatment with protons. Not all patients who are recommended by their oncologists to undergo such radiotherapy receive an invitation for treatment. In each case, the specialists of the proton therapy center evaluate the risks for the patient during photon therapy and the prognosis of the disease when using proton therapy. Experts believe that only 15% of all patients with various types of cancer should receive proton rather than photon radiotherapy.

There are currently 110 proton therapy centers in the world. Most of them are in the USA and Japan. The price of proton therapy in these countries is very high, so the treatment is not available to most foreign patients.

Proton therapy can be done in South Korea, India and China. There are 27 centers in Europe, including in Italy, Austria and Spain. For example, the centers MedAustron and Quiron Salud. The most demanded by foreign patients are several proton therapy centers in Germany and the Proton Therapy Center in Prague. They have both advanced proton irradiation technologies and well-known oncologists and radiologists. In addition, experience has been gained in the treatment of foreign patients with various types of cancer. At the same time, each center, despite the high international standard of proton cancer treatment, has its own characteristics. Therefore, it is not always possible to independently make the right choice in favor of a particular center.

It is best to ask for help in this matter from the operator who organizes the treatment in proton therapy centers, for example, Experts Medical. Medical coordinators will help to conduct initial consultations in several centers. To do this, they will prepare, translate and transfer the necessary medical documents, including the results of CT and MRI. After receiving an invitation for treatment, they will provide information about how much proton therapy and related services cost, and answer all questions regarding treatment at the center of your choice.

Experts Medical specialists organize travel and accommodation near the proton therapy center and provide comprehensive support during treatment. In addition, they will help pay for part of the cost of proton therapy for a child with the help of charitable foundations with which Experts Medical cooperates.