What is proton therapy?
Proton therapy is a form of radiation therapy that destroys cancer cells by preventing them from dividing and growing—the same as with standard X-ray radiation. Proton therapy uses protons—positively charged atomic particles—instead of the photons used in standard X-ray radiation therapy.
Protons can be precisely conformed so that much of their energy is released directly in the tumor, greatly reducing damage to nearby healthy tissue. As a result, patients generally have far fewer side effects from treatment and may be able to receive higher, more effective doses.
How does proton therapy work?
Protons can be controlled to release their energy at precise depths so they can target tumors inside the body, depositing much of their radiation exactly at the tumor site. The peak of this proton-radiation dose (called the Bragg Peak) is set so it deposits the radiation at the tumor site; the radiation dose falls to almost zero beyond the treated volume. Less radiation is deposited in the healthy tissue in front of the tumor, and almost none reaches the healthy tissue behind the tumor, resulting in much less damage to healthy tissue. Patients often experience fewer of the short- and long-term side effects that typically accompany standard X-ray radiation. In addition, because more radiation can be deposited directly in the tumor, a higher dose can often be delivered, leading to more effective treatment.
How do proton beams destroy cancer cells?
When protons reach the nucleus (or 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.
Is proton therapy experimental?
No, proton therapy is not experimental. Proton therapy was approved by the U.S. Food and Drug Administration (FDA) to treat patients in 1988. Its first medical application was in the mid-1950s and it has been used to treat patients since. Medicare and Medicaid began covering the procedure in 2000. To date, almost 70,000 people worldwide have received proton therapy at centers in Europe, Asia, and the United States.
What is the history of proton therapy?
In 1946, physicist Robert Wilson first proposed that protons could be used to deliver an increased dose of radiation to a tumor while simultaneously decreasing the exposure of surrounding healthy tissue to radiation.
By the 1950s, research trials were being conducted on patients in the U.S. and Europe. Results were promising, but the inability of imaging technology to accurately "see" or locate many tumors, as well as the inability to direct protons to sites deep within the body, meant that only a few patients were appropriate candidates for the treatment.
Advances in imaging, including computed tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET), now allow physicians to "see" deep inside the body and precisely define the location, size, and shape of tumors. This capability, coupled with improvements in proton technology, brought about today's growing interest in proton therapy as an important treatment option for cancer.
The first hospital-based proton treatment center in the United States was completed in 1990 at Loma Linda University Medical Center (LLUMC) in Loma Linda, California. As of October 2010, 9 facilities are operating in the United States: CDH Proton Center, A ProCure Center, in Illinois; ProCure Proton Therapy Center, Oklahoma City, Oklahoma; Francis H. Burr Proton Therapy Center at Massachusetts General Hospital; the Midwest Proton Radiotherapy Institute at Indiana University; the Proton Therapy Center at the M.D. Anderson Cancer Treatment Center in Texas; The Roberts Proton Therapy Center at the University of Pennsylvania; the Florida Proton Therapy Institute at the University of Florida Shands Medical Center; Loma Linda University Medical Center in California; and Hampton University Proton Therapy Institute in Virginia. In addition, there is a specialty proton center that treats only cancers of the eye at the University of California, Davis.
When was proton therapy first used for medical purposes?
Proton therapy was first used to treat patients in the United States in Berkeley, California, in the 1950s. 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 cancer tumors. Accurately locating tumors made it possible to leverage the precision of protons. The first U.S. center opened at Loma Linda University Medical Center in 1990. More than 20 centers have opened in the past 20 years, and by 2008, there were 29 centers worldwide.
How many patients have received proton therapy?
Since the first hospital-based proton treatment center opened in California in 1990, nearly 30,000 people have received proton therapy in the United States, and almost 70,000 people worldwide. Experts conservatively estimate that about 250,000 cancer patients in the United States could benefit from proton therapy.
What kinds of studies have been/are being done to prove the effectiveness of proton therapy?
The effectiveness of proton therapy has been studied by researchers around the world. A growing number of studies report on the effectiveness of proton therapy and its benefits compared to alternative treatments. The amount of research being conducted on proton therapy is rapidly increasing as more centers open and more patient experiences become available.
See Clinical Literature Bibliography »
Can proton therapy be used in combination with other cancer treatments?
In many cases, yes. Proton therapy can be used in combination with chemotherapy, as a follow-up treatment to surgery, and in combination with standard X-ray radiation treatment.
What are the potential side effects of proton therapy?
Your patients should not feel pain or discomfort during treatment sessions. Side effects may occur 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. This is 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 tumor site treated, different side effects may be experienced. If you or your patients have questions about the specific side effects that they may experience, please contact our centers. We are available via phone or email for your convenience.
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Is there currently a clinical trial on proton therapy?
Yes, the medical community continues to conduct research studies on proton therapy. Major institutions like MD Anderson Cancer Center and Massachusetts General Hospital have many ongoing clinical trials to help find improvements in treating cancer with proton therapy. ProCure centers are currently participating in two clinical trials. One is a Phase III randomized trial comparing the effects of standard radiation dose and a higher daily dose of proton radiation in patients with low-risk prostate cancer, the other is an evaluation tracking project that collects and analyzes information from patients who have been treated with proton therapy. For more information on these trials, please click here.
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PROTON THERAPY CLINICAL INDICATIONS
What are some of the common tumor sites treated with proton therapy?
Certain types of cancer are more appropriate for proton therapy than others. While research continues to support using protons in more types of tumors, they are primarily used to treat:
- Prostate cancer
- Brain tumors
- Pediatric tumors
- Head and neck tumors
- Gastrointestinal (GI) cancers
- Base-of-skull tumors
- Juxtaspinal cord tumors
- Non-small-cell lung cancer
- Paranasal sinus tumors
- Ocular (uveal) melanoma
- Arteriovenous malformations (AVM)
Proton therapy is particularly appropriate for treating tumors in children, who typically experience more serious short- and long-term side effects from radiation treatments than adults.
Learn more about tumor sites that can benefit from proton therapy.»
Can proton therapy be used for all types of cancers in all patients?
Proton therapy is not appropriate for all types of cancers or all patients. It is most effective on solid tumors (including but not limited to those found in the head, brain, neck, lung, and prostate) that are well-defined and localized—those that have not spread to other areas of the body. However, each case is affected by a tumor’s size, location, and numerous other variables, so each should be evaluated on a case-by-case basis.
Why is proton therapy only an option for certain types of cancer?
Because of the limited number of proton-treatment facilities worldwide, physicians have focused on using proton therapy primarily for tumors near critical organs, such as the heart and bladder, or structures, such as the spine. The types of tumors treated will continue to expand as research continues and doctors develop treatment plans for more types of tumors.
Can proton therapy be used to treat children with cancer?
Yes, in fact proton therapy is particularly effective for children who need radiation therapy. Clinical studies indicate that proton therapy reduces the risk of growth and developmental problems as well as the risk of secondary tumors, which can occur years later. Because a child’s body is small and still growing, the damage to nearby healthy tissue and organs from standard X-ray radiation can be harmful. This damage can cause growth abnormalities, reductions in IQ, and other complications. New tumors can also develop later in the child's life. A growing body of research is confirming the advantages of the use of proton therapy for children.
Can proton therapy be used to treat recurrent cancers?
In many cases, yes. Proton therapy can be used to treat recurrent cancers that standard X-ray radiation therapy cannot. In addition, patients treated with proton therapy can be retreated, unlike patients treated with standard radiation who can only receive a single course.
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Comparing protons and photons (X-rays)
How is proton therapy different from standard radiation treatment?
Proton therapy is more precise than standard radiation treatment. With proton therapy, much of the energy is deposited directly into the tumor, reducing damage to surrounding healthy tissue and allowing patients to receive higher, more effective doses. Less damage to healthy tissue and organs can result in fewer side effects than are sometimes experienced with standard X-ray radiation therapy, thus improving patients' quality of life and long-term health. X-ray radiation can be harder to control and deposits more radiation in healthy tissue as it enters and leaves the body.
Are X-rays (photons) as effective as protons in destroying tumors?
X-rays and protons are equally effective in destroying cancer tumors. The difference is that X-ray treatments damage more healthy tissue in the process. X-rays release much of their energy quickly after penetrating the skin, damaging healthy tissue and organs on their way to the tumor and, again, as they leave the body. Protons can be precisely directed so that much of their energy is released when they reach the tumor. Because there is much less damage to healthy tissue, it may be possible to deliver a higher dose with protons, leading to more effective treatment.
Why is proton therapy often considered a better treatment option compared to standard X-ray radiation therapy?
Because protons deposit more of their energy directly in the tumor, less radiation reaches the healthy tissue in front of the tumor, and almost none reaches the healthy tissue behind the tumor, proton therapy is often considered a better treatment option. Patients often experience fewer of the short- and long-term side effects that typically accompany standard X-ray radiation therapy. In addition, because more radiation can be deposited directly in the tumor, a higher dose can often be delivered, leading to more effective treatment.
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