Radiation therapy, sometimes called radiotherapy, is the careful use of high energy x-rays to safely and effectively treat cancer. This treatment is directed to the tumor area and to any neighboring tissues felt to be at risk of containing tumor cells. It does not go all over the body. Radiotherapy can be used in rectal cancers to control cancer growth. Depending upon the location and stage of the cancer, the doctor may recommend a combination of chemotherapy and radiation either before or after the surgery.
Radiation given before surgery (preoperative or neoadjuvant therapy) can help shrink the tumor. Shrinking the tumor before surgery may reduce the need for more extensive surgery. In tumors that are located low in the rectum or near the anus, the surgeon may be able to avoid removing the anal sphincter, preventing the need for a permanent colostomy.
Radiation therapy given after the surgery helps keep the cancer from coming back. This kind of treatment will be recommended for large tumors that have a higher risk of regrowth and recurrence. Radiation in this timeframe does not begin until four to eight weeks after surgery in order to allow the wounds to adequately heal. The radiation is then delivered to the area near the surgical site and the local lymph nodes. This treatment, referred to as external beam irradiation, is usually delivered through the outside of the body to the internal areas where the tumor was found.
Radiation therapy is given as daily outpatient treatments Monday through Friday for a period of five to six weeks. A treatment planning session is done before this treatment begins and involves use of a CT scan to map out exactly where the radiation therapy should be delivered.
