Colon and Rectal Cancers - Radiation Treatment

Radiation Treatment

Radiation therapy uses x-rays to kill cancer cells that might remain after an operation or to shrink large tumors before an operation so that they can be removed surgically. The object of radiation therapy is to damage the tumor as much as possible without harming surrounding tissues. Radiation may be administered in the following ways:

• Externally by an x-ray machine (external beam radiation).
• By passing radioactive pellets through thin plastic tubes inserted into the intestine.
• By implanting tiny radiation seeds directly into the tumor (brachytherapy).
• Computer imaging techniques providing 3-dimensional pictures of the cancerous area are allowing precise targeting of radiation to the tumor.

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Postoperative Radiation with Chemotherapy for Rectal Cancer

Postoperative radiation treatment combined with chemotherapy is common practice for patients with rectal cancer in Stages II and III. Such patients are at risk of recurrence both at the site of their original tumor and elsewhere in the body. Although there can be significant long-term side effects, the combination of 5-FU and radiation is still considered standard after surgery.

Preoperative Radiation

The standard procedure in the U.S. is to apply radiation after surgery (postoperative). Preoperative chemotherapy and radiation, however, are sometimes used to preserve sphincter-muscle function and reduce the chance that a patient will require a colostomy. Furthermore, some studies suggest that the use of radiation before surgery reduces the likelihood of recurrences and may slightly prolong survival in some patients with rectal cancer. (It has no additional advantages, however, if the subsequent surgery does not completely remove the cancerous regions.) Studies comparing preoperative and postoperative chemotherapy and radiation are currently under way.

Intra-Operative Radiotherapy (IORT)

Radiation therapy is also being used during surgery (a procedure called intra-operative radiotherapy). It allows the surgeon to move healthy tissue out of the path of the radiation beam.

Side Effects of Radiation Therapy

Short-term side effects of radiation include:

• Diarrhea
• Skin irritation around the anus
• Incontinence
• Fatigue
• Bowel movement problems

Longer-term complications may include:

• Incontinence
• Hip and pelvic fractures
• Diarrhea
• Increased risk for bowel obstruction

Review Date: 03/06/2007
Reviewed By: A.D.A.M. Editorial Team: Greg Juhn, M.T.P.W., David R. Eltz, Kelli A. Stacy. Previously reviewed by Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital (9/1/2006).

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