What is radiation?

You might hear you’re getting radiation treatment. But what is it, exactly?

Radiation oncologists use beams of high energy to alter and damage the DNA in cancer cells, ultimately killing them. These beams come from a highly specialized machine, and are aimed directly at your tumor. You will not see or feel the beams going into your body during treatment.

Radiation can also affect healthy cells, although side effects may take a few days to set in. Radiation therapy takes time to work, and will continue to work in the body for several weeks after treatment has finished.

How is radiation used to treat colorectal cancer?

Radiation treatment can be used:

• Before, after, or during surgery to kill any cancer cells left over and prevent the tumor from coming back
• As a palliative measure, if a patient is unable to undergo surgery or if the tumor is causing pain or a blockage
• To treat metastases in the lungs, brain, bones, liver, or other areas
• As a local treatment done concurrently with systemic treatment — like chemotherapy or immunotherapy

Radiation is more commonly used to treat primary rectal cancer than colon cancer. If you have been diagnosed with rectal cancer, it’s more likely that radiation will be part of your treatment plan. This is because most of the rectum does not have a protective peritoneal covering that encircles the colon. This makes it more likely for a rectal tumor to break through and spread locally in the pelvic cavity (the space between your pelvic bones). Tumors here are difficult to treat with surgery.

If surgery is a part of your treatment plan, you will likely have radiation first to help kill cancer cells, shrink the tumor, and make it easier for your surgeon to get all of the cancer while sparing the healthy parts of your rectum.