Proton therapy

Most types of radiation therapy use x-rays to destroy cancer cells. Proton therapy uses a beam of special particles called protons. Proton beams can be better aimed onto a tumor, so there is less damage to the surrounding healthy tissue. This allows a higher dose of proton therapy to be used than can be used with x-rays.

Proton therapy is used to treat cancers that have not spread. Because it causes less damage to healthy tissue, proton therapy is often used for cancers that are very close to critical parts of the body.

Proton therapy may be used to treat the following types of cancer:

• Brain (acoustic neuroma, childhood brain tumors)
• Eye (ocular melanoma, retinoblastoma)
• Head and neck
• Lung
• Spine (chordoma, chondrosarcoma)
• Prostate
• Lymph system cancer

Researchers are also studying whether proton therapy might be used to treat other noncancerous conditions, including macular degeneration.

HOW IT WORKS

A member of the radiation therapy team will fit you with a special device that holds your body still during treatment. The actual device used depends on the location of your cancer. For example, people with head cancers may be fitted for a special mask.

Next, you will have a computed tomography (CT) or magnetic resonance imaging (MRI) scan to map out the exact area to be treated. During the scan, you will wear the device that helps you stay still. The radiation oncologist will use a computer to trace the tumor and outline the angles at which the proton beams will enter your body.

Proton therapy is performed on an outpatient basis. The treatment takes a few minutes a day over a period of 4 to 7 weeks, depending on the type of cancer. Before the treatment begins, you will get into the device that will hold you still. A member of your care team will take a few x-rays to fine-tune the treatment before each daily session.

You will lie down flat on a table that can be placed inside a donut-shaped device called a gantry. It will rotate around you and point the protons in the direction of the tumor. A machine called a synchrotron or cyclotron creates the protons, and using a series of magnets, speeds up the protons to accurately deliver the protons to the tumor.

The technician will leave the room while you are having proton therapy but can see and hear you on the monitors. The treatment should only take 1 to 2 minutes. You should not feel any discomfort. After the treatment is over, the technician will return to the room and help you remove the device that held you still.

SIDE EFFECTS

Proton therapy may have side effects, but these tend to be milder than with x-ray radiation because proton therapy causes less damage to healthy tissues. Side effects depend upon the area being treated, but may include skin redness and temporary hair loss in the radiation area.

AFTER THE PROCEDURE

Following proton therapy, you should be able to resume your normal activities. You will likely see your health care provider every 3 to 4 months for a follow-up exam.

Proton beam therapy; Cancer - proton therapy; Radiation therapy - proton therapy; Prostate cancer - proton therapy; IMPT (intensity modulated proton therapy)

National Association for Proton Therapy website. Frequently asked questions. proton-therapy.org/patient-resources/faq/. Accessed July 6, 2024.

Shabason JE, Levin WP, DeLaney TF. Charged particle radiotherapy. In: Gunderson LL, Tepper JE, eds. Gunderson and Tepper's Clinical Radiation Oncology. 5th ed. Philadelphia, PA: Elsevier; 2021:chap 24.

Zeman EM, Schreiber EC, Tepper JE. Basics of radiation therapy. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 27.

Updated by: David Herold, MD, Radiation Oncologist in Jupiter, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.