What is Proton Therapy & How Does It Work in the Treatment of Cancer?

Proton therapy works on the principle of ‘radiation treatment’ which makes use of Proton’s radiation to treat cancer. Proton is a positively charged particle, the radiations of which are focused on the cancer cells, at high energy. Since the therapy makes use of Proton, therefore Proton therapy is also known as Proton Beam Therapy.

Depending upon the type of cancer, Oncologists may use proton therapy alone or in combination with other treatment, surgery, immunotherapy, chemotherapy or in adjunction with other radiation therapy.

Proton Therapy is a therapy that involves the use of external beam radiations. The treatment makes use of a machine called as cyclotron or synchrotron that delivers radiation through the skin, painlessly. The depth of the proton radiations inside the body is determined by the energy levels of the protons. Higher the speed of protons, greater are its energy levels and therefore the depth of the radiations in the body shall also be high.

The proton radiations are targeted onto a particular point of the body where the tumor exists. The dose of protons required to penetrate the tumor is pre-decided based on the size of the tumor and its spread in the body.

The best thing about Proton Therapy as compared to other radiation therapy is that in proton therapy the radiations do not go beyond the tumor however in other radiation therapies especially the photon based external beam radiation therapy, the rays deposit the radiations in the body before moving out of the body. These radiations thereby damage the nearby healthy tissues and thus lead to the development of side effects.

The other benefit of proton therapy in the treatment of cancer is that it can be carried out in an outpatient setting. Therefore, the patient does not need to stay in the hospital, overnight.

Like any other radiation therapy, proton therapy also requires proper planning. The proton therapy can be delivered in either 2-5 sessions or can be administered in single but large radiation dose. The decision is made based on several factors including the age, height, weight of the body, severity of the cancer etc. The radiation therapy given in 2-5 sessions is termed as stereotactic body radiation therapy and the radiation therapy in which a single but large radiation dose is given is called as radiosurgery.

Before initiating the radiation therapy session, a magnetic resonance imaging scan (MRI) or a computed tomography scan (CT scan) is done to detect and mark the area which requires the treatment. This helps in aiming the radiations effectively each time the patient goes for the proton therapy sessions.

During the scan, the patient’s body is positioned in a similar manner, as it would be during the proton therapy session. Since positioning is very important during the scan as well as the radiation session, therefore immobilization devices are used to restrict the movement of the body. The type of immobilization device depends upon the location of the tumor. In certain cases, custom made immobilization masks may be required if the tumor is present in brain, eyes or head. Get in touch with your radiation oncologist to feel comfortable or reduce anxiety during the scanning or radiation session.

1. The treatment is carried out in a special room where the members of the radiation oncology team place the patient on a treatment table with the help of immobilization device.
2. The body is aligned as per the mark or the dot placed during the CT scan or MRI scan. The dot along with the scan images helps in planning the proton therapy session effectively.
3. After setting the patient’s body in the desired position, the oncologist radiologist team leave the room. From outside the room, the team remains in touch with the patient via an audio or video equipment and using the controls present in the entrenchment area outside the room, initiate the proton radiation therapy
4. As the radiation leaves the synchrotron or cyclotron machine, the magnetic force generated with the help of magnets, present in the machines, is used to direct the radiations to the tumor. During this time, the fixed position of the body ensures the effective targeting of the radiations to the spot marked during the initial scan.

Alternatively, some radiation oncologist may make use of gantry during the radiation. The benefit of using the gantry is that it can rotate easily and deliver the radiation from an angle, as prescribed by the Oncologist.

The treatment may last for about 15 to 30 minutes once the patient enters the room but the time may vary depending upon a number of factors which are listed below:-

• Number of treatment segments
• The parts of the body, receiving the treatment
• Number of prerequisite x-rays done before initiating the treatment
• Availability of the number of synchrotron or cyclotron machine at the facility. If the machines are less and the patient beds are more, the patient might have to wait for the session.

Although Proton Therapy is painless, however, the patient may experience some side effects of proton therapy as the release of energy takes place inside in the body.

Following are some of the side effects that a patient may experience post proton therapy session:-

• Fatigue
• Skin problems such as swelling, dryness, redness, peeling, blistering or irritation
• Headache
• Loss of hair
• Urge to vomit
• Nausea
• Digestion problem

The intensity of side effects from proton therapy may vary depending upon the following factors:-

• Size of the tumor
• Number of proton therapy sessions
• Part of the body receiving the proton therapy session
• The health condition of the neighboring tissues to the tumor.

Proton therapy can help in treating the following types of cancers:-

• Proton therapy is used to treat tumors that are present near the important body parts like the brain, eye, spinal cord etc. especially if it occurs in children. The damage caused due to the proton therapy radiation cause less harm to the healthy, sensitive and developing tissues
• Liver cancer
• Eye Cancer including choroidal melanoma or uveal melanoma
• Lung Cancer
• Non-cancerous brain tumor
• Prostate cancer
• Neck and head cancer including paranasal sinus and nasal cavity as well as nasopharyngeal cancer
• Pelvic sarcomas
• Spinal sarcomas

Get in touch with your Oncologist to discuss more about the treatment plan and the number of proton therapy sessions that would be required. Also, request him to prescribe you medications, so as to manage the side effects, if caused, post proton therapy session. Always remember, “Your illness does not define you, your courage and strength does”. Therefore fill your mind with powerful thoughts and your inner self would automatically start healing your body.

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