Radiation Therapy

Steve Banks, M.D. Radiation Oncology

Q: What is radiation therapy?
Radiation therapy is the medical use of high energy x-rays that can kill cancer cells. Radiation therapy is an integral component of treatment for many patients with rectal cancer. Its uses include shrinking tumors to improve the chances that they can be surgically removed, treating areas near the rectum which are either known to be involved by the cancer or at high risk of involvement, or treating any areas where cancer could not be surgically removed.

Radiation therapy reduces the risk of rectal cancer recurring in the pelvis, and it improves the chance of being cured of rectal cancer. It can also be used to reduced symptoms caused by spread of rectal or colon cancer to other sites of the body.

Q: How is radiation therapy administered?
Radiation for rectal cancer is typically administered by a large x-ray machine, called a linear accelerator which aims a beam of radiation directed at the cancer. This is called external beam radiation. This beam is shaped using special shields or blocks to spare excessive treatment of normal healthy tissues. Each treatment takes 5-10 minutes and is as painless as a chest x-ray. Now developments have allowed for major improvements in our ability to target cancerous tissues and spare healthy ones.

End-cavity radiation, in which an x-ray beam is directly applied to a rectal tumor through a tube or a radioactive pellet is placed directly into close proximity to the rectal tumor, is also used in special circumstances.

Q: Is radiation therapy used alone or in combination with surgery and chemotherapy?
For some rectal cancers, radiation alone can be very effective treatment. More typically, however, it is used in conjunction with chemotherapy either before or after surgery. In these scenarios, it reduces the risk of the cancer returning in the pelvis, and studies have also shown that this treatment can improve the chance of surviving rectal cancer.

Q: Is radiation therapy given all at once or over a period of time?
Because radiation affects normal healthy cells as well as cancer cells, radiation is typically given in multiple small doses. This takes advantage of the increased sensitivity of cancer cells to the killing effects of the radiation as well as the increased ability of healthy cells to heal the injury caused by small doses of radiation. For rectal cancer, a typical course of radiation involves a daily treatment, five days a week, for 5-6 ½ weeks.

Q: Are there side effects to radiation therapy?
Unfortunately, radiation therapy can cause side effects including nausea, diarrhea, loss of appetite, fatigue, and skin changes. If side effects are severe, the radiation therapy regimen can be altered to allow the patient to recover. Side effects usually subside when radiation therapy ends. There is a small risk of permanent side effects.

Resources
Radiation Therapy Effects