Radiation therapy uses high-energy sub-atomic particles to disrupt the cell division mechanism of cancerous cells. Radiation therapy for prostate cancer may be used as an initial treatment for an early-stage tumor that remains confined to the prostate or has only started to invade nearby tissues. Radiation oncologists administer the treatments using external machines, or internally by depositing the radiation source through needles or catheters into the tumor. Proton beam therapy is an external radiation therapy that uses protons rather than x-rays to destroy cancer cells.
How It Works
Standard x-ray radiation deposits most of the energy of the beam near the body's surface, causing unnecessary damage to healthy tissues. Protons, however, can be energized to specific velocities. As the protons pass through tissues, they slow down, until they reach a velocity where the energy is released and becomes absorbed. By calculating the depth of the tumor and rate of decline in velocity as the beam travels through tissues, the radiation oncologist can deposit the bulk of the beam energy at a specific depth in the body. This allows release of the maximum cell-destroying energy dose within the tumor mass. As a result of this ability to control the proton dose distribution, the doctor can increase the radiation dose to the tumor with much less harm to healthy tissues.
Effectiveness
The American Cancer Society says that proton beam therapy for prostate cancer has shown promising results in early clinical studies, but there is not enough data to say whether proton beam therapy is more or less effective than current treatments. The Prostate Cancer Foundation says proton beam therapy appears to be most effective for treating localized, isolated, solid tumors.
Side Effects
Centers performing proton beam therapy have reported that the treatment generally causes fewer and milder side effects than other forms of external beam radiation therapy for prostate cancer. The exact extent of side effects, however, is unknown because there have been no head-to-head comparison trials. Side effects of standard external beam radiation therapy for prostate cancer include urinary, bowel and sexual effects that can be temporary or long-term. Other side effects of prostate radiation therapy include fatigue and lymphedema, a build up of lymph fluid in the pelvis or legs if the lymph nodes are irradiated.
Benefits
The National Association for Proton Therapy says the primary advantage of proton beam therapy is that it is the most precise form of radiation therapy available. It is painless, minimizes the usual side effects of external beam radiation, and treatment takes as little as one day or only as long as eight weeks depending on tumor sites. Patients can usually maintain their quality of life during treatment.
Access and Availability
The Prostate Cancer Foundation notes that the primary disadvantages of proton beam therapy are cost and access. The machines that produce protons can cost as much as $150 million, consequently, there are less than a dozen centers in the United States offering proton beam therapy, as of 2010. While efforts to reduce these costs and increase availability are underway, it remains to be seen whether the benefits are significant enough to warrant the cost of building and installing proton beam therapy facilities.
Considerations
Although the cost of receiving proton beam therapy is about 50 percent higher, and currently few health insurers are covering it, it is gaining wider acceptance. In addition to the cost of the treatment, patients also need to consider travel and lodging costs to a treatment center. There also may be significantly longer waits for scheduling treatment due to the small number of treatment centers open.
