Frequently asked questions
With less side effects, longer life expectancies, reduced secondary cancers and promising results, proton therapy has the potential to change cancer treatment as we know it. Learn more about the next generation of cancer care.
What is proton therapy?
Not unlike standard X-ray radiation, proton therapy is a form of radiation treatment that destroys cancer cells by preventing them from dividing and growing. The difference, however, is that proton therapy uses protons — heavy, positively-charged atomic particles — instead of the photons used in standard X-ray radiation therapy.
This is more effective because protons can be precisely conformed to release most of their energy directly into the tumor, greatly reducing damage to nearby healthy tissue. As a result, patients can often receive higher, more effective doses and generally have fewer side effects — both long-term and short-term.
How does proton therapy work?
Protons can be manipulated to release their energy at precise depths, so they are able to target tumors near the skin surface or deep inside the body, depositing most of their radiation exactly at the tumor site. The peak of this proton radiation dose — referred to as the Bragg peak — is programmed to release the radiation when it hits the tumor. The dose then, almost immediately, falls to almost zero. Less radiation reaches the healthy tissue in front of the tumor, and only a negligible amount reaches the healthy tissue behind the tumor, resulting in far less damage to healthy tissue.
How do proton beams destroy cancer cells?
When protons reach the nucleus (center) of cancer cells, they transfer energy to the cells’ electrons causing a series of interactions, or ionizing events, that damage the DNA of the cancer cells. The damaged cells are permanently injured, can no longer divide, and die.
What are the potential side effects of proton therapy?
Patients should not feel pain or discomfort during treatment sessions. There may be side effects during or after treatment, but they are generally minor, less frequent and less severe than the side effects that can result from standard X-ray radiation therapy, primarily because less healthy tissue is exposed to radiation in proton therapy.
Potential side effects may include skin reactions in the direct path of the proton radiation, fatigue and temporary hair loss. Depending on the site of the tumor being treated, additional side effects may vary. Your doctor will discuss the specific side effects that you may experience based on your treatment plan.
Can proton therapy be used in conjunction with other cancer treatments?
In many cases, yes. Proton therapy can be used in conjunction with chemotherapy, as a follow-up treatment to surgery, and in combination with standard X-ray radiation treatment.
When was proton therapy first used for medical purposes?
Proton therapy was first used to treat patients in a research setting in Berkeley, California, in 1955. While promising, it wasn’t until advances in imaging technology, such as CT, MRI and PET scans, allowed doctors to accurately “see” the location, size and shape of tumors. Accurately locating tumors made it possible to leverage the precision of protons.
The first U.S. proton therapy practice opened in California at Loma Linda University Medical Center in 1990, and there are now nearly 60 such facilities worldwide with several others currently in the development or construction phase.
How many patients have received proton therapy?
Since the first hospital-based proton treatment center opened in 1990, nearly 30,000 people have received proton therapy in the United States, and more than 60,000 people worldwide. Experts conservatively estimate that about 250,000 cancer patients in the U.S. could benefit from proton therapy.
Although demand is high in the U.S., the limited number of treatment facilities has made it difficult for patients to receive proton radiation therapy. The current annual capacity of existing proton centers in the U.S. is about 8,000 patients
Have any studies been conducted to determine the effectiveness of proton therapy?
The effectiveness of proton therapy has been studied by researchers around the world, and there is a growing number of reports that indicate proton therapy and its benefits are superior to those associated with alternative treatments.
Clinical evidence has shown protons to be associated with improved outcomes (the obliteration of malformations) and reduced side effects when compared to X-ray therapy. A 2008 MGH study also determined that proton therapy patients are 50% less likely to develop a secondary cancer.
The amount of research being conducted on proton therapy is rapidly increasing as more centers open and more patient experiences become available.