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 one of the following two ways:
The main use for radiation therapy in people with colon cancer is when the cancer has attached to an internal organ or the lining of the abdomen. When this occurs, the surgeon cannot be certain that all the cancer has been removed, and radiation therapy may be used to kill any cancer cells remaining after surgery. Radiation therapy is seldom used to treat metastatic colon cancer because of side effects, which limit the dose that can be used.
For rectal cancer, radiation therapy is usually given to help prevent the cancer from coming back in the pelvis where the tumor started. It may be given either before or after surgery, but recently doctors have begun to favor preoperative treatment, along with chemotherapy. If a rectal cancer's size or position make surgery difficult, radiation may be used before surgery to shrink the tumor. Radiation therapy can also be given to help control rectal cancers in people who are not healthy enough for surgery.
Radiation also may be used to ease (palliate) symptoms in people with advanced cancer causing intestinal blockage, bleeding, or pain.
Radiation treatment is often combined with chemotherapy. Chemotherapy helps make the radiation treatment more effective. Radiation therapy is more often used for rectal cancer but may also be used in some cases for colon cancer.
Radiation for Colon Cancer. Radiation for colon cancer is given after surgery (postoperative or adjuvant radiation) to destroy any remaining cancer cells. It is generally not used to treat metastatic colon cancer.
Radiation for Rectal Cancer. Adjuvant radiation is a common practice for patients with rectal cancer in Stages II and III. Radiation is used to help prevent cancer recurrence. In recent years, doctors have also begun administering chemotherapy and radiation before surgery for rectal cancer (neoadjuvant chemoradiation). The use of radiation before surgery can help shrink the size of the tumor. Pre-operative chemotherapy and radiation may also help preserve sphincter-muscle function and reduce the chance that a patient will need a colostomy.
Side effects of radiation may include:
Botteri E, Iodice S, Raimondi S, Maisonneuve P, Lowenfels AB. Cigarette smoking and adenomatous polyps: a meta-analysis. Gastroenterology. 2008 Feb;134(2):388-95. Epub 2007 Nov 4.
Ciardiello F, Tortora G. EGFR antagonists in cancer treatment. N Engl J Med. 2008 Mar 13;358(11):1160 74.
Figueredo A, Coombes ME, Mukherjee S. Adjuvant therapy for completely resected stage II colon cancer. Cochrane Database Syst Rev. 2008 Jul 16;(3):CD005390.
Johnson CD, Chen MH, Toledano AY, Heiken JP, Dachman A, Kuo MD, et al. Accuracy of CT colonography for detection of large adenomas and cancers. N Engl J Med. 2008 Sep 18;359(12):1207-17.
Jonker DJ, O'Callaghan CJ, Karapetis CS, Zalcberg JR, Tu D, Au HJ, et al. Cetuximab for the treatment of colorectal cancer. N Engl J Med. 2007 Nov 15;357(20):2040-8.
Karapetis CS, Khambata-Ford S, Jonker DJ, O'Callaghan CJ, Tu D, Tebbutt NC, et al. K-ras mutations and benefit from cetuximab in advanced colorectal cancer. N Engl J Med. 2008 Oct 23;359(17):1757-65.
Kim DH, Pickhardt PJ, Taylor AJ, Leung WK, Winter TC, Hinshaw JL, et al. CT colonography versus colonoscopy for the detection of advanced neoplasia. N Engl J Med. 2007 Oct 4;357(14):1403-12.
Kuhry E, Schwenk WF, Gaupset R, Romild U, Bonjer HJ. Long-term results of laparoscopic colorectal cancer resection. Cochrane Database Syst Rev. 2008 Apr 16;(2):CD003432.
Imperiale TF, Glowinski EA, Lin-Cooper C, Larkin GN, Rogge JD, Ransohoff DF. Five-year risk of colorectal neoplasia after negative screening colonoscopy. N Engl J Med. 2008 Sep 18;359(12):1218-24.
Levin B, Lieberman DA, McFarland B, Smith RA, Brooks D, Andrews KS, et al. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA Cancer J Clin. 2008 May-Jun;58(3):130-60. Epub 2008 Mar 5.
Moghaddam AA, Woodward M, Huxley R. Obesity and risk of colorectal cancer: a meta-analysis of 31 studies with 70,000 events. Cancer Epidemiol Biomarkers Prev. 2007 Dec;16(12):2533-47.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Colon Cancer. V.3.2008
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Rectal Cancer. V.3.2008.
U.S. Preventive Services Task Force. Routine aspirin or nonsteroidal anti-inflammatory drugs for the primary prevention of colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2007 Mar 6;146(5):361-4.
U.S. Preventive Services Task Force. Screening for colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2008 Nov 4;149(9):627-37. Epub 2008 Oct 6.
Weinberg DS. In the clinic. Colorectal cancer screening. Ann Intern Med. 2008 Feb 5;148(3):ITC2-1-ITC2-16.
Wolpin BM, Mayer RJ. Systemic treatment of colorectal cancer. Gastroenterology. 2008 May;134(5):1296-310.
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