Radiation Therapy for Prostate Cancer

External Beam Radiation Therapy

External beam radiation therapy (also called radiotherapy) involves a series of daily treatments to accurately deliver radiation to the prostate. There are several ways to deliver external beam radiation. Recently completed research trials have shown that increasing the dose of radiation can be done safely with improvement in outcome and avoidance of significant side effects.

• Before treatment, you will have a scan to allow the radiation oncologist to target the radiation on the cancer. Usually several radiation beams are combined to shape, or “conform”, the radiation to the prostate cancer. This technique is called three-dimensional conformal radiation therapy or 3D-CRT. Tailoring each of the radiation beams to accurately focus on the tumor allows doctors to target the prostate cancer while keeping radiation away from nearby organs such as the bladder or rectum.
• Some doctors use a type of 3D-CRT called intensity modulated radiation therapy or IMRT. IMRT allows doctors to change the intensity of the radiation within each of the radiation beams, allowing doctors to safely increase the amount of radiation to the prostate. Sometimes this is done with image guided radiation therapy (IGRT), a technique using direct visualization of the prostate anatomy before each daily treatment.
• In a few clinics in the country, proton beam therapy is used to treat prostate cancer. Proton therapy is a form of external beam radiation that uses protons rather than photons (X-rays) to treat cancer cells. Proton therapy is precise like IMRT, only it uses a different kind of radiation.
• Each of these treatments is acceptable. With all external beam therapy, painless radiation treatments are delivered in a series of daily sessions, each about 15 minutes long, Monday through Friday, for six to 10 weeks. The duration of your treatment will depend on your health and the type of radiation used.
• The use of even shorter schedules of external beam radiation therapy is being studied for patients with early-stage prostate cancer. Stereotactic body radiation therapy (SBRT) is a technique for treating cancers in five or fewer treatments that is not yet considered a standard treatment option for prostate cancer. It is the subject of ongoing investigations. ASTRO's Emerging Technology Committee recently published a report on SBRT for prostate cancer in April 2010 that you may want to discuss with your radiation oncologist if you are considering this treatment.
• More about external beam radiation therapy