Radiation treatment is the use of high-energy rays (such as x-rays) to kill cancer cells or shrink tumors. The radiation may come from outside the body (external radiation) or from radioactive materials put right in the tumor (brachytherapy or internal or implant radiation).
After surgery, radiation can kill small areas of cancer that may be missed during surgery. If the size or place of a tumor makes it hard to take it out, radiation may be used before surgery to shrink the tumor. Radiation can also be used to ease symptoms of advanced cancer, such as intestinal blockage, bleeding, or pain.
The main use for radiation treatment in people with colon cancer is when the cancer has attached to an internal organ or the lining of the belly (abdomen). If this happens, the doctor can't be sure that all the cancer has been removed, and radiation is used to kill the cancer cells left behind after surgery. Radiation is seldom used to treat metastatic colon cancer.
For rectal cancer, radiation is often given either before or after surgery to help prevent the cancer from coming back in the place where it started.
External-beam radiation therapy: In this treatment, radiation is focused on the cancer from a machine outside the body. This is the type most often used for people with colon or rectal cancer. Treatments are given 5 days a week for many weeks. Each treatment lasts only a few minutes, but the setup time -- getting you into place for treatment -- usually takes longer.
A different approach may be used for some cases of rectal cancer with small tumors. A small device can be put into the anus to deliver the radiation. This way the radiation reaches the rectum without passing through the skin and other tissues of the abdomen. This means it is less likely to damage nearby tissues and cause side effects.
Brachytherapy (internal radiation therapy): In this method, small pellets or seeds of radioactive material are placed next to or right into the cancer. The radiation travels only a short distance, limiting the effects on nearby healthy tissues. This method is sometimes used in treating people with rectal cancer, particularly sick or older people who would not be able to go through surgery.
Some patients who have a lot of spread to the liver but little or no spread to other distant parts of the body may get treatment with infusion through the artery that goes to the liver. The doctor injects tiny glass "beads" that are coated with a radioactive atom (yttrium-90). These beads block some of the small blood vessels that feed the tumors and their radioactivity helps kill the cancer cells.
Side effects of radiation therapy
Side effects of radiation therapy for colon or rectal cancer include skin soreness, nausea, diarrhea, trouble controlling your bowels, rectal or bladder irritation, and tiredness. Sexual problems may also occur. Side effects often go away over time after treatment is over. If you have these or other side effects, talk to your doctor. There are often ways to reduce or relieve many of these problems.
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