What is Radiation Therapy?
Radiation is the strategic use of ionizing radiation or photons to kill cancer cells. It works by damaging the cancer cells’ DNA (the genetic blueprint of the cancer cell).The targeted cells die without growing or replicating themselves. Radiation therapy, like surgery, is very effective at killing localized or locally advanced prostate cancer and has the same cure rate as surgery.
Just as surgical skill can play an important role in determining outcomes from prostatectomy, the technical skill of your radiation oncologist can play an important role in radiation outcomes. When choosing a radiation oncologist, look for a physician who has broad experience with an assortment of approaches and can objectively help you decide on the best course of treatment.
External Beam Radiation Therapy (EBRT)
EBRT is the most common type of radiation therapy. In EBRT, CT scans and MRIs are used to map out the location of the tumor cells, and X rays are targeted to those areas. Your “mapping” scan will help your radiation oncologist to locate the precise anatomy of your prostate, rectum, and bladder so that radiation dosimetrists and physicists can work with sophisticated computer treatment systems to design a personalized radiation plan for you: exactly how much radiation to deliver, exactly where to focus it, and how often the treatments should be. There are many types of EBRT, each with its own advantages and disadvantages.
Review the types of EBRT with the Prostate Cancer Patient Guide.
Since radiation therapy is non-invasive (unlike surgery), there is no down time or healing time. You can be physically active every day of treatment and in the months following. It is common to have mild increased frequency of urination or bowel movements during the weeks of treatment. These symptoms generally begin to improve 2 to 4 weeks after the end of the treatment course. Many studies have shown that while surgery results in a more immediate loss of erectile function followed by a period of partial recovery, radiation therapy results in a slower loss of erectile function over time in men who had good erectile function before treatment.
EBRT Treatment Durations
There are 3 common treatment durations, or number of treatments, that are used in EBRT:
- Conventional: For decades, radiation therapy has been delivered every day (Monday through Friday), for a total of 35-45 treatments
- Moderate hypofractionation: Recently, clinical trials that have shown that as few as 20 treatments in 4 weeks can have similar cure rates and side effects as conventional radiation over 8 to 9 weeks. In hypofractionation, the doses given each day are higher than conventional dose level
- Ultra-hypofractionation: Also known as stereotactic body radiation therapy (SBRT), this type of treatment is delivered in just 5 sessions. These doses are even higher than with hypofractionated therapy. This strategy is rapidly becoming more common because it has lower side effects, equal cure rates, and increased convenience. However, not all centers provide this treatment, and not all patients are good candidates, so make sure to consult your doctor. This type of radiation therapy has been compared head-to-head with the traditional 8 to 9 week course of radiation and shown to have similar cure rates and side effects.
Brachytherapy involves placing radiation therapy “seeds” or temporary catheters inside the prostate that emit radiation at a very short distance.
Think of it as internal radiation therapy, rather than external radiation therapy. Radioactive seeds (LDR or low dose rate) or catheters (HDR or high dose rate) are inserted directly into the prostate while you are asleep under anesthesia. It is usually done in 1 to 4 treatment sessions depending on the method used. The seeds are permanently placed into your prostate, while the catheters are only temporarily placed inside the prostate and then removed after treatment is done. LDR brachytherapy kills the cancer over many months as the seeds give off radiation to the immediate surrounding area, thus killing the prostate cancer cells. By the end of the year, the radioactive material degrades, and the seeds that remain are harmless.
Brachytherapy by itself is usually used only for low- risk or favorable intermediate-risk patients. It is usually combined with some form of external beam radiation and often hormone therapy for higher-risk patients. The success of brachytherapy, like surgery, is dependent on the skill of your practitioner. Ask your doctor to help you find an experienced radiation oncology team who can perform brachytherapy.
Compared with external radiation therapy, brachytherapy is now used less often, but some patients prefer this option primarily because it doesn’t require daily visits to the treatment center. Side effects can include erectile dysfunction, urinary frequency and obstruction, and rectal injury. Patients with large prostates or those patients with a lot of urinary problems are usually poor candidates for brachytherapy. Additionally, patients will need to speak with their doctor regarding restrictions on holding infants in their lap after the procedure.