If you've been diagnosed with prostate cancer and are exploring your treatment options, you've probably come across proton beam therapy (PBT) -- an increasingly popular form of external radiation treatment that promises fewer side effects. However, only a few centers offer it, and some experts don't believe it's superior to other advanced radiation treatments. Here's what you need to know.
Many men choose radiation to treat their prostate cancer because, unlike other treatments, such as prostatectomy (prostate removal), there is no hospitalization or surgical risk, no restriction of activities during or after the procedure, no need for a catheter, and a low risk of urinary incontinence.
Doctors use 3-D imaging (e.g., computed tomography [CT] and magnetic resonance imaging [MRI] scans) to help aim radiation directly at the tumor. But since standard radiation therapy is delivered by x-rays, which deposit energy on entering and exiting the body, both the cancer cells and some surrounding healthy tissue are exposed to radiation.
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PBT is unique because it uses protons (small subatomic particles) instead of x-rays to treat cancer. While conventional x-rays tend to "spread" like the light from a flashlight, in PBT most of the proton energy is released at the end of a narrow proton beam, so only a small area of healthy tissue between the skin and the tumor is exposed.
Despite its benefits, some experts argue that PBT isn't necessary because of the now widespread use of 3-D intensity-modulated radiotherapy (IMRT). IMRT radiation is broken up into thousands of tiny beams that enter the body from many angles and intersect at the tumor. Much like PBT, IMRT allows very precise aim, resulting in a higher radiation dose to the tumor and a lower dose to surrounding tissue.
No clinical trials directly compare PBT and IMRT. But IMRT is less expensive than PBT, and some experts argue that no data indicate PBT is more effective than IMRT, even at higher doses. The Centers for Medicare and Medicaid Services reviewed all the evidence surrounding PBT and decided to continue covering the cost of this treatment for prostate cancer because it has proven benefits, despite the lack of direct evidence from clinical trials comparing PBT and IMRT.
Practical Issues. While most experts concede PBT is superior to older forms of radiation and is at least as effective as IMRT, only 1% of prostate cancer patients receive it. The reason? The proton accelerator that provides the radiation is the size of a football field and costs $100-200 million to build.
Nationwide, there are only five PBT facilities. Most men who get PBT are under age 65 and have localized, low-intermediate-grade prostate cancer. In the few centers that offer PBT, space for these patients is limited: PBT treats other types of cancer, too, and priority is given to children and patients with rare, inoperable tumors or other conditions that can't be treated any other way. Therefore, more than half of patients who apply for PBT are turned away.
This situation is changing, though, as many proton centers are under pressure to treat increasing numbers of people with common cancers to turn a profit and repay investors. Many centers are connected to special hotel/spa facilities where people receiving PBT can opt to stay.
Proton Beam Therapy Centers: Proton beam therapy centers can be found in each major region of the United States. Additionally, four new centers are under construction and one is in the planning stages.
- Midwest Proton Radiotherapy Institute at Indiana University Bloomington, IN (812) 349-5074 www.mpri.org
- University of Florida Proton Therapy Institute Jacksonville, FL (877) 686-6009 www.floridaproton.org
- University of Texas MD Anderson Cancer Center Houston, TX (877) 636-6789 www.mdanderson.org
- Francis H. Burr Proton Therapy Center at Massachusetts General Hospital Boston, MA (617) 726-0923 www.massgeneral.org/radiation oncology/BurrProtonCenter.aspx
- James M. Slater, M.D. Proton Treatment and Research Center at Loma Linda University Medical Center Loma Linda, CA (800) PROTONS (776-8667) www.protons.com
