Protection by endoscopy against death from colorectal cancer. A case-control study among veterans.

BACKGROUND: Although several clinical and epidemiologic studies suggest that timely diagnostic procedures of the large bowel may reduce mortality from colorectal cancer, the evidence for this relationship is primarily circumstantial.

METHODS: A case-control study was conducted among hospitalized US military veterans to investigate whether diagnostic procedures of the large bowel were performed in the period preceding the diagnosis of colorectal cancer less frequently in patients dying of colorectal cancer than in control patients. Data files of a total of 4411 veterans dying of colorectal cancer between 1988 and 1992 were extracted from the records of the US Department of Veterans Affairs, Washington, DC. Data of four living control patients and four dead control patients without colorectal cancer were matched by age, sex, and race to each case patient. The case and the two control populations were compared by conditional logistic regression, calculating odds ratios, and their 95% confidence interval.

RESULTS: Diagnostic procedures of the large bowel reduced mortality from colorectal cancer, the odds ratio being 0.41 (range, 0.33 to 0.50) for the comparison with living control patients. The protective effects of proctosigmoidoscopy, colonoscopy, and polypectomy lasted for 5 years. The procedures were protective against death from cancer of the colon, as well as cancer of the rectum. The most protective influence was associated with removal of tissue through biopsy, fulguration, and polypectomy. Similar influences were found comparing case patients with dead control patients.

CONCLUSION: Removal of tissue represents the most effective means to reduce mortality from cancers of the large bowel. It retains its efficacy over a time period of 5 years.