How is radiation therapy used to treat colorectal cancer?

Radiation isn't typically used to treat colon cancer, says Ovunc Bardakcioglu, MD, a colon and rectal surgeon at Sunrise Hospital. In this video, he discusses which therapies are used to treat the disease.

Radiation therapy uses high-energy rays (such as x-rays) or particles to destroy cancer cells. It may be part of treatment for either colon or rectal cancer. Chemotherapy can make radiation therapy more effective against some colon and rectal cancers, and these 2 treatments are often used together.
In people with colon cancer, radiation therapy is mainly used when the cancer is found to have attached to an internal organ or the lining of the abdomen. When this occurs, the surgeon cannot be certain that all the cancer has been removed, and radiation therapy may be used to try to kill any cancer cells that may remain after surgery. Radiation therapy is seldom used to treat metastatic colon cancer because of side effects, which limit the dose that can be used.
For rectal cancer, radiation therapy is usually given either before or after surgery to help prevent the cancer from coming back in the area where the tumor started. It is often given along with chemotherapy. Many doctors now favor giving radiation therapy before surgery, as it may make it easier to remove the cancer, especially if the cancer's size and/or position may make surgery difficult. Giving radiation before surgery may lower the risk that the tumor will come back (recur) in the pelvis. It may also result in fewer complications such as scar formation that can cause problems with bowel movements. Radiation therapy can also be given to help control rectal cancers in people who are not healthy enough for surgery or to ease (palliate) symptoms in people with advanced cancer causing intestinal blockage, bleeding, or pain.

Radiation Oncology uses high-energy x-rays to kill cancer cells, and is a common treatment for rectal cancer due to these tumors' tendencies to locally recur. It may be used both before and after surgery, either to shrink a tumor or to kill any post-operative cells that may be left. Doctors may also use radiation in conjunction with chemotherapy before surgery to reduce both incidences of colostomy as well as a tumor's chance of recurrence.

Since radiation can damage healthy cells in addition to cancerous ones, there is a risk of certain side effects, including fatigue, skin irritation and damage at the site where the treatment is given, loss of appetite, nausea, and diarrhea, as well as bloody stools (bleeding through the rectum) or bowel obstruction. Sexual problems and infertility may also arise after pelvic radiation treatments.