Increased age may be associated with a shorter survival time. Women have a better prognosis than men in general. The CRC prognosis worsens when moving from the right to the left side of the colon. Histologic grading and operative findings are important prognostic factors for CRC. Nodal involvement is an essential component of both the Dukes and the TNM staging systems. Poorly differentiated histology is associated with a poorer prognosis compared to well-differentiated histology. The 5-year survival rate is most favorable for CRC of the descending colon and rectum. The overall 5-year survival figures after surgery for CRC Dukes A is 70% to 83%, Dukes B 48% to 62%, and Dukes C 22% to 33%.
Prevention of colon cancer remains a theoretic possibility and ought to be pursued, especially for patients whose family histories place them at high risk. Identifying genetic predisposition, dietary modifications, cessation of alcohol and tobacco use, and chemoprevention represent the spectrum of preventive modalities.
None of these has proved to be completely effective for preventing CRC. The role of genetic predisposition in CRC is most prominent for patients with familial polyposis, inflammatory bowel disease, a family history of colon cancer, and a family history of adenomatous polyps. The first two categories require aggressive and regular surveillance to identify the development and removal of early adenomas up to and including total colectomy. Siblings and parents of patients with adenomatous polyps are at an increased risk for CRC, particularly when the adenoma is diagnosed before the age of 60 or, in the case of siblings, when a parent has CRC. Some recommend screening with colonoscopy or ACBE the first-degree relatives of patients with adenomatous polyps diagnosed before age 60. The American Cancer Society recommends colonoscopy or ACBE every 3 to 5 years starting at age 35 to 40 for patients with a first-degree relative having CRC with an age of onset of 55 or less. Screening should be earlier for patients with familial polyposis syndrome, a family history of nonpolyposis CRC, or inflammatory bowel disease. If patient has colorectal adenomas, they should be removed. When an adenoma is found on flexible sigmoidoscopy, colonoscopy must be done to detect and remove all polyps. Most patients with history of adenomas require colonoscopy every 3 to 5 years. Individualized evaluation is necessary for the aged and for patients with a malignant adenoma, multiple adenomas, or a sessile adenoma. Genetic testing is available for patients at risk for familial adenomatous polyposis (FAP). A patient with a negative genetic test has essentially zero risk for FAP, whereas a patient with a positive genetic result has a 100% likelihood of developing FAP.
Chemoprevention has shown significant signs of promise. Recent observations suggest that aspirin and other NSAIDs, supplemental folate and calcium, and postmenopausal hormone replacement therapy (estrogen) have a chemopreventive benefit. Although encouraging, the value of chemoprevention has not yet been substantiated through more extensive study and should not replace standard screening techniques or risk-reducing lifestyle changes.
Gregory L. Brotzman and Russell G. Robertson
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