Note: Separate PDQ summaries on Colorectal Cancer Screening; Colorectal Cancer Prevention; and Genetics of Colorectal Cancer are also available. Information about colon cancer in children is available in the PDQ summary on Unusual Cancers of Childhood Treatment.

Note: Estimated new cases and deaths from rectal cancer in the United States in 2008:[1]

• New cases: 40,740.
• Deaths (colon and rectal cancers combined): 49,960.

Note: Some citations in the text of this section are followed by a level of evidence. The PDQ editorial boards use a formal ranking system to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for more information.)

Cancer of the rectum is a highly treatable and often curable disease when localized. Surgery is the primary treatment and results in cure in approximately 45% of all patients. The prognosis of rectal cancer is clearly related to the degree of penetration of the tumor through the bowel wall and the presence or absence of nodal involvement. These 2 characteristics form the basis for all staging systems developed for this disease. Preoperative staging procedures include digital rectal examination, computed tomographic scan or magnetic resonance imaging scan of the abdomen and pelvis, endoscopic evaluation with biopsy, and endoscopic ultrasound (EUS).[2] EUS is an accurate method of evaluating tumor stage (up to 95% accuracy) and the status of the perirectal nodes (up to 74% accuracy). Accurate staging can influence therapy by helping to determine which patients may be candidates for local excision rather than more extensive surgery and which patients may be candidates for preoperative chemotherapy and radiation therapy to maximize the likelihood of resection with clear margins. The American Joint Committee on Cancer and a National Cancer Institute-sponsored panel recommended that at least 12 lymph nodes be examined in patients with colon and rectal cancer to confirm the absence of nodal involvement by tumor.[3,4,5] This recommendation takes into consideration that the number of lymph nodes examined is a reflection of both the aggressiveness of lymphovascular mesenteric dissection at the time of surgical resection and the pathologic identification of nodes in the specimen. Retrospective studies demonstrated that the number of lymph nodes examined in colon and rectal surgery may be associated with patient outcome.[6,7,8,9] Many other prognostic markers have been evaluated retrospectively in the prognosis of patients with rectal cancer, though most, including allelic loss of chromosome 18q or thymidylate synthase expression, have not been prospectively validated.[10,11,12] Microsatellite instability, also associated with hereditary nonpolyposis rectal cancer, has been shown to be associated with improved survival independent of tumor stage in a population-based series of 607 patients less than 50 years of age with colorectal cancer.[13] Racial differences in overall survival after adjuvant therapy have been observed, without differences in disease-free survival, suggesting that comorbid conditions play a role in survival outcome in different patient populations.[14] A major limitation of surgery is the inability to obtain wide radial margins because of the presence of the bony pelvis. In those patients with disease penetration through the bowel wall and/or spread into lymph nodes at the time of diagnosis, local recurrence following surgery is a major problem and often ultimately results in death.[15] The radial margin of resection of rectal primaries may also predict for local recurrence.[16]