Radiation Therapy for Colorectal Cancer

Colon cancer is typically treated with surgery and chemotherapy but radiation therapy (or radiotherapy) may be an important part of your treatment plan if you have advanced disease. Radiotherapy treatments may also be used as palliative care to ease cancer symptoms.

Radiation therapy uses high-energy x-rays to kill cancer cells. The radiation kills cancer cells using oxidizing molecules that disrupt important cell functions. Normal cells are better able to withstand and survive radiation therapy than cancer cells. Radiation therapy for colorectal cancers may be delivered in different ways, including:

• External beam radiation therapy (EBRT) is the most common method of delivering radiation for treatment of colorectal cancer. Radiation is usually delivered over 25-28 treatments and can be done in several ways, each with its own advantages.
• 3-dimensional conformal radiation therapy (3D CRT) is a form of EBRT where a few shaped radiation beams are aimed at the cancer target from different directions.
• Volumetric modulated arc therapy (VMAT) is a more precise form of EBRT than 3D CRT, where the field shape is changed continuously as the treatment machine moves around the patient, delivering the radiation. This treatment helps to spare normal tissue.
• Chemoradiation therapy combines chemotherapy and external beam radiation therapy by starting the treatments on the same day. The chemotherapy drugs sensitize cancer cells to the effects of the radiation, leading to increased tumor-killing effects. The medical and radiation oncologists on your team work together to plan and prepare your treatment for maximum benefit.
• Intraoperative radiation therapy (IORT) delivers radiation in the operating room to the surgical margins immediately after the surgeon removes the cancer. This treatment kills potential microscopic disease at the surgical margin and is especially beneficial when tumors are next to a blood vessel and the surgeon cannot take any more tissue.