Chapter Overview 85
Principles of Screening 87
Current Screening Recommendations and Limitations 88
Fecal Occult Blood Testing 88
Flexible Sigmoidoscopy 91
Barium Enema 91
Investigational Measures for Colorectal Cancer Screening 94
Colon Cancer Chemoprevention 95
Groups at High Risk for Colorectal Cancer as Targets for
Chemoprevention Trials 95
COX-2 Inhibition in Patients with Sporadic Colorectal
The Future 101
Key Practice Points 101
Suggested Readings 102
Colorectal cancer is one of the most common and serious cancers. The predictable adenoma-to-carcinoma sequence and the relative accessibility of the colon to available screening measures allow many opportunities for early detection and prevention. Accepted screening measures include testing for fecal occult blood, barium enema, flexible sigmoidoscopy, and more recently, colonoscopy. Newer screening techniques include computed tomography colonography and stool-based DNA testing. All of the above have to do with early detection and, in the case of colonoscopy, treatment of early colorectal neoplasia. Because these are still secondary prevention measures, primary prevention through "chemoprevention" is a focal point at M. D. Anderson Cancer Center and elsewhere. Epidemio-
logic and experimental background have provided a basis for recent clinical trials demonstrating a role for nonselective and selective cyclo-oxygenase-2 inhibition of adenoma progression in an important human condition, familial adenomatous polyposis. One ongoing trial involves use of a combination of agents (celecoxib and difluoromethylornithine) with different proposed mechanisms of action: COX-2 inhibition and ornithine decarboxylase inhibition. Another trial is investigating the role of COX-2 inhibition in potentially delaying onset of first adenomas in young carriers of APC gene mutations responsible for familial adenoma-tous polyposis.
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