Rectal Cancer (cont.)

Radiation therapy uses high-energy rays that are aimed at the cancer cells to kill or shrink them. For rectal cancer, radiation therapy may be used either before surgery (neoadjuvant therapy) or after surgery (adjuvant therapy), usually in conjunction with chemotherapy.

The goals of radiation therapy are as follows:

• Shrink the tumor to make its surgical removal easier (if given before surgery).
  
  
• Kill the remaining cancer cells after surgery to reduce the risk of the cancer returning or spreading.
  
  
• Treat any local recurrences that are causing symptoms, such as abdominal pain or bowel obstruction.

Typically, radiation treatments are given daily, 5 days a week, for up to 6 weeks. Each treatment lasts only a few minutes and is completely painless; it is similar to having an x-ray film taken.

The main side effects of radiation therapy for rectal cancer include mild skin irritation, diarrhea, rectal or bladder irritation, and fatigue. These side effects usually resolve soon after the treatment is complete.

Chemoradiation is often given for stages II and III rectal cancer. Preoperative chemoradiation is sometimes performed to decrease the size of the tumor.