Proton therapy – cancer treatment of the 21st century

Proton therapy is a type of radiation therapy that is used to treat many types of cancer and some benign tumors. Currently, proton therapy is considered the safest and most gentle method of radiotherapy, therefore it is widely used in the treatment of cancer in children.

However, this option of radiation therapy has not only advantages but also certain limitations. Therefore, the decision to travel abroad for expensive proton cancer treatment must be informed and balanced.

What is proton therapy? What cancer needs proton therapy? Can proton irradiation cure cancer? Where it is possible to get this treatment? We will consider the answers to these and other questions in detail in this article.

What do you need to know about proton therapy?

This type of radiotherapy uses proton beams. Such radiation is produced in special proton linear accelerators - synchrophasotrons. Ionizing radiation obtained by accelerating hydrogen nuclei (protons) is directed at the malignant tumor. Penetrating into cancer cells, proton beams ionize and destroy their DNA. As a result, malignant cells lose their ability to divide and the tumor stops growing.

Proton therapy has been used to treat cancer for more than 30 years. The procedure is carried out only in specialized centers with large, heavy- weight, complex and expensive equipment and numerous qualified experienced personnel. In recent years, due to technical improvements in proton therapy facilities, it has been possible to reduce their multi-ton weight and cost, which has increased the availability of this cancer treatment method: new proton therapy centers are opening around the world.

Systems for delivering a dose of ionizing radiation to tumors are also constantly being improved. Several years ago, second-generation proton irradiation technology was introduced into clinical practice. “Pencil beam scanning (PBS)” allows you to irradiate a cancer tumor as accurately as possible.

How is proton irradiation different from conventional radiotherapy?

Both standard radiation therapy and proton radiotherapy damage the DNA of cancer cells. It is carried out in much the same way: radiotherapists carry out planning using a 3D model of the tumor based on CT and MRI data. The number of radiation sessions varies from 1-2 (radiosurgery) to 35 (daily fractionated radiotherapy).

In this context, there are significant differences. In conventional radiotherapy, gamma rays are used to target tumors, generated by linear accelerators using photons and electrons. Despite advanced techniques for precisely directing the radiation beam to the cancerous area and treatment methodologies, gamma rays begin releasing energy immediately upon entering the human body. As a result, healthy tissues, structures, and organs both before and after the tumor are ionized (exposed) to some extent during their entire path through the body. This leads to undesirable short-term and long-term side effects and complications for the patient. Consequently, radiation therapists often cannot apply maximum therapeutic doses.

Proton therapy, on the other hand, utilizes protons, which possess a unique characteristic: they release minimal destructive energy and impact healthy tissues only along the path to the cancerous tumor. Only when they reach the predetermined depth specified by the radiologist do they deliver the full radiation dose and then stop (this phenomenon is known as the “Bragg peak”). Thanks to these characteristics, proton therapy offers significant advantages compared to conventional radiotherapy.

What is the main advantage of proton therapy?

The main advantage of proton treatment is its safety for healthy tissue. With proton therapy, healthy tissues and internal organs receive 60% less ionizing radiation, and a malignant tumor receives 30% more than with photon radiotherapy. (data from the American Association of Clinical Oncologists). Especially when using PBS proton irradiation technology. Therefore, treating cancer with proton beams opens up new possibilities for radiotherapists.

When undergoing proton therapy, the vast majority of patients maintain a satisfactory quality of life and normal activity. If adverse reactions occur, they are usually short-term and reversible. It is obvious that proton therapy, compared to traditional radiotherapy, has a more gentle effect on the body during irradiation.

In addition, reducing the ionizing effect on the bone marrow allows patients to undergo chemotherapy, including high-dose chemotherapy, simultaneously with proton irradiation. This increases the effectiveness of treatment and medical chances in the fight against cancer.

What does proton therapy treat?

Proton therapy has already shown high effectiveness in many types of cancer in both adults and children. Radiotherapists have increasingly begun to consider proton therapy as a more promising option for a wide range of cancer diseases.

Proton therapy for oncology in adult patients

Proton therapy is indicated for tumors located in areas of the body where irradiation of healthy tissue leads to serious complications. These are the central nervous system, red bone marrow, gonads, gastrointestinal tract and other radiosensitive organs and systems. Proton therapy can be successfully used as an alternative to surgical treatment for cancer of the brain, esophagus, spine, and prostate gland.

A retrospective study from the US National Cancer Database found that lung cancer patients who received proton therapy had better survival than patients treated with conventional radiotherapy. For inoperable cancers with metastases, proton irradiation in combination with chemotherapy, targeted and immunotherapy can significantly improve the condition of patients and prolong life. Proton therapy is the best radiation treatment option for all types of cancer in younger patients.

Proton therapy is the optimal method for treating cancer in children

The growing child’s body consists of rapidly developing tissues, which makes it more susceptible to radiation therapy and the development of short-term and long-term side effects. In children, these effects often have irreversible consequences. Among them, the most undesirable is the development of secondary radiation-induced cancer caused by exposure to radiation.

Reducing the radiation burden on a child’s body is achieved through proton therapy. Therefore, when treating malignant tumors in children, especially those located close to vital organs such as the brain, spinal cord, eyes, and heart, proton therapy is the preferred form of radiation treatment. Studies based on mathematical modeling and data on the impact of ionizing radiation on the human body have shown that the risk of developing secondary cancer is 4 to 10 times higher with photon radiotherapy compared to proton irradiation. When assessing the risks associated with radiation exposure in patients with medulloblastoma, it was calculated that the likelihood of developing radiation-induced tumors is significantly lower (4%) with proton therapy than with photon radiation (30%).

Treatment of children is carried out in the same proton therapy centers where adults are treated. Currently, in many centers, more than 50% of all patients are children under 18 years of age.

What types of cancer can only proton therapy help with?

In 2017, the American Society of Radiation Oncology (ASTRO) published guidelines for the use of proton therapy. This treatment is recommended for patients with tumors of the organs of vision, spinal cord, base of the skull, and hepatocellular cancer. And also to all pediatric patients and patients who need a second course of radiation therapy for cancer recurrence.

Proton therapy is most widely used for chordomas and chondrosarcomas of the skull base. These tumors cannot be removed surgically and are dangerous to irradiate with conventional radiation therapy due to their location near the brain stem. The use of a proton beam in this case makes it possible to deliver sufficient radiation doses for an antitumor effect without damaging vital brain structures. For retinal melanoma, only proton radiation therapy can save the eye and vision.

How much does proton therapy cost?

The list of the most expensive cancer treatments includes proton therapy.

Proton therapy course price

The cost of a course of treatment, on average, is $50,000. Obviously, the cost of proton therapy for oncology is 2-3 times higher than the cost of the most high-tech and expensive option of photon radiation therapy, like CyberKnife. This is due to the fact that a proton accelerator for cancer treatment is an expensive and complex machine to operate. This is a “supersonic Concorde” compared to conventional linear accelerators. Therefore, proton therapy centers are only available in highly developed countries with advanced but expensive medicine.

If your oncologist recommends proton therapy

In this case, given the cost of a course of proton therapy, it is better to consult simultaneously in 2-3 specialized centers that have advanced radiation technologies and accept citizens of other countries for treatment. In such centers, there is a careful selection of patients using special prognostic models that help assess the risks of photon therapy and the benefits of proton therapy in each specific case. This allows you to predict the outcome of treatment. After comparing all the offers, you can choose the most suitable option.

You can organize such consultations and help make the most correct decision, as well as organize the trip itself, using the Experts Medical service: coordinating doctors have the relevant experience and expertise. Another significant advantage of turning to these specialists is Experts Medical’s cooperation with charitable foundations, which help pay part of the cost of proton treatment for cancer in a child.

Sources:

• https://pubmed.ncbi.nlm.nih.gov/27979443/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4256116/
• https://pubmed.ncbi.nlm.nih.gov/16165914/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5303653/
• https://www.proton-therapy.org/
• https://www.cancer.gov/news-events/cancer-currents-blog/2020/proton-therapy-safety-versus-traditional-radiation