External beam radiation therapy (EBRT) uses high-energy rays to kill cancer cells and shrink tumors. EBRT is the principal treatment for locally advanced prostate cancer, and it affects cells only in the treated area. The radiation comes from a large machine outside the body that aims high-energy x-rays at the cancer site. Treatments are usually given 5 days a week and may last 8-9 weeks. Adding ADT to radiation treatment may improve survival time by killing cancer cells that have spread outside the prostate gland.

A high-tech form of radiation therapy that is guided by a computer — known as 3-dimensional conformal radiation therapy or intensity-modulated radiation therapy — allows the treatment to closely follow the shape of the prostate, reducing the risk of damage to tissue outside the target area. This type of therapy allows your doctor to see the size and shape of the tumor and give the highest possible dose of radiation to the tumor from different angles. Radiation may also be directed at pelvic lymph nodes if there is a high risk for spread of the disease.

If you have certain medical conditions, such as inflammatory bowel disease, or a permanent indwelling urinary catheter, radiation cannot be done. In addition, radiation therapy is not recommended if you have any of the following problems:

Chronic moderate or severe diarrhea
Inactive ulcerative colitis
Very low bladder capacity
Bladder outlet obstruction requiring a suprapubic catheter

A short course of radiation therapy is also an effective way to relieve pain if cancer has spread to your bones. If the pain is widespread, radioactive medications called radiopharmaceuticals are often successful in relieving bone pain. Strontium 89 (Metastron) and samarium 153 (Quadramet) are radioactive injections that can be given intravenously (through a vein) for metastatic bone pain. These medicines collect in bones where cancer is located, and may slow cancer growth as well as relieve pain. There is a risk, however, of bone marrow suppression (reduced ability to produce blood cells), which might limit other treatments.

You may have heard of brachytherapy or proton beam therapy, but neither is effective treatment for advanced prostate cancer.

Side Effects

Side effects depend on the dose and type of radiation used. Tiredness is typical, especially in the later weeks of treatment. Diarrhea and frequent urination or burning with urination may occur. Skin in the treated area may become dry, red, and tender, and you may lose hair in the area, which may not grow back. In the later weeks of treatment, radiation may cause inflammation of the lining of the bladder, rectum, or small intestine, resulting in urinary and bowel problems such as frequent urination or retention of urine and incontinence (inability to hold urine or bowels). Impotence may also occur in the later stages of treatment. Be sure to tell your doctor of any side effects you experience with radiation treatment.

Monitoring Response

It can be difficult to strike a balance between effective disease control and living with side effects that can be hard to tolerate. Monitoring the PSA level and pain symptoms provides information about the effectiveness of treatment. After radiation therapy, the PSA level should fall to less than 0.5 ng/mL. Generally, an increase in the PSA level on two consecutive tests indicates that the treatment has failed. After radiation therapy, it is recommended that the PSA level be checked every 6 months. A DRE is recommended at least every year. Your doctor will want to know about any concerns or new symptoms you experience after treatment.

Questions about Radiation Therapy You May Want to Ask Your Doctor

Which type of radiation is an option for me?
How often will I have treatments? How long will they last?
How will I feel during the treatments?
How will I feel when the treatments are done?
Will my activities be limited?
Will I need to stay in the hospital?
What are the side effects? Are there any long lasting effects?
What is the chance that the cancer will come back?
How often will I need checkups once treatment is over?