- Proton therapy is usually painless, and you can often return to your daily activities afterward.
- A typical course of treatment is five days per week for several weeks.
- The proton beam only treats you for a few minutes, but preparation and positioning take longer.
What is proton therapy?
Proton therapy, also known as proton beam therapy, is a form of radiation treatment used to destroy tumor cells. Instead of using x-rays like regular radiation treatment, it uses protons to sends beams of high energy that can target tumors more precisely than X-ray radiation.
When treating a patient, doctors and physicists work together to focus the proton beam on the exact size and shape of the tumor. The beam kills the tumor cells layer by layer, sparing surrounding healthy tissue.
How Proton Beam Therapy Works
Proton therapy is an advanced form of radiation treatment that uses protons instead of X-rays.
In regular radiation therapy, the beam of energy goes into the body, through the tumor, and out the other side. This “exit dose” of radiation might affect healthy tissue beyond the tumor. Protons, in contrast, are larger particles than those used in regular radiation. They release more of their energy within the tumor itself. This burst of energy can appear on a graph as what is called the Bragg peak.
After delivering the energy to the tumor, the protons stop: They do not exit the tumor and go into healthy tissue on the other side.
In this way, proton therapy reduces radiation exposure and potential damage to healthy tissue, especially in sensitive areas such as the brain, eyes, spinal cord, heart, major blood vessels and nerves.
What is it like to get proton therapy?
Proton therapy is an outpatient procedure. Most patients are treated over a course of several sessions, and some treatments take longer than others. Currently, the proton beam is only available in a few specialized centers.
Getting Ready for Proton Therapy
Proton therapy involves careful planning to make sure the proton beam hits its target. You might undergo imaging tests such as computed tomography or MRI to provide pictures of the tumor and the surrounding area before each session. The therapy team might make marks on your body to highlight the treatment area — these are mostly temporary.
The proton treatment takes place in a special room. In some centers, a large mechanical arm called a gantry can move the beam around you as you lie on a table. This helps the radiation therapists treat the tumor from several angles.
Depending on the size, location and number of tumors, you will spend about 15 to 30 minutes in the treatment room.
Positioning for Proton Beam Treatment
Positioning the body is very important. It can take several minutes for the team to adjust both you and the instruments to make sure the proton beam will reach the exact spot of the tumor.
While the treatment is happening, you must be very still on the table. The team will work with you to help keep you in place. For example, a custom-fitted mask can help those who are getting treatment for brain tumors. The mask is made of mesh that allows patients to see and breathe.
What Happens During Proton Beam Treatment
Once you are ready and in position, the therapists will leave the room so they can operate the proton beam machine. A video camera helps them see and hear you so you will not be alone.
The treatment itself takes only a few minutes. A large machine speeds up protons and creates energy. The proton beam focuses this energy into the body, at the precise depth where the tumor is located. The gantry might move around your body and treat the tumor from several positions.
You will not feel the proton beam as it enters the body or as it is treating the tumor.
Proton Therapy Side Effects
After your session, you might feel tired. Proton therapy side effects are similar to those of other radiation treatment methods. Because the technique can mean less exposure to the radiation, side effects can be less than those of traditional radiation treatment.
Side effects can develop gradually after treatment, and might include:
- Sore, reddened skin around the treatment area that can look and feel like a sunburn
- Hair loss in the treatment area
- Tiredness or low energy
Additional side effects, depending on the area treated, can include headaches and problems with eating and digestion.
Recovery from Proton Therapy
After being treated with the proton beam, most people can go home and resume their activities. For certain tumors, your doctor might order tests to see how the treatment is affecting the tumor, and adjust your treatment if necessary.
The Johns Hopkins National Proton Center
Located at Sibley Memorial Hospital in Washington, D.C., our center combines advanced proton therapy technology, the latest research and caring specialists who provide tailored treatments for a variety of adult and pediatric cancers.
Which tumors might be treated with proton therapy?
Proton therapy is used to treat cancerous and non-cancerous tumors in children and adults. It can be especially valuable when addressing brain and spinal cord tumors in children, who often suffer lasting side effects from toxic cancer treatments.
Proton beams can be used to treat:
- Sarcomas, particularly those in the base of the skull, spine or the retroperitoneum
- Breast cancer
- Prostate cancer
- Rhabdomyosarcoma, melanoma and other cancers around the eye
- Lung cancer and other thoracic cancers such as lymphoma or thymoma
- Head and neck cancer
- Liver cancer
- Pancreatic cancer
- Benign tumors
Researchers are studying the potential benefits of proton beam therapy on other kinds of cancers.
What are the benefits of proton therapy?
Both regular and proton radiation therapy damage the DNA of cancer cells, but proton therapy has two main advantages: more energy focused on the tumor, and less radiation affecting healthy tissue nearby.
With less healthy tissue affected by the radiation, side effects can be milder. Damage to delicate structures such as the brain, heart, oral cavity, esophagus and spinal cord might be reduced.
What are the disadvantages of proton therapy?
Proton therapy is not appropriate for every type of cancer. It is best suited for cancers in sensitive areas, where other treatments might damage surrounding healthy cells.
The machines and equipment for proton therapy are very complex and expensive to make and operate. It is important to check with your insurance provider about coverage. Some proton therapy centers have financial counselors to consult.
Your doctor will recommend the appropriate treatment for your cancer.