Colonoscopic polypectomy and long-term prevention of colorectal-cancer deaths

Abstract

Background: In the National Polyp Study (NPS), colorectal cancer was prevented by colonoscopic removal of adenomatous polyps. We evaluated the long-term effect of colonoscopic polypectomy in a study on mortality from colorectal cancer.

Methods: We included in this analysis all patients prospectively referred for initial colonoscopy (between 1980 and 1990) at NPS clinical centers who had polyps (adenomas and nonadenomas). The National Death Index was used to identify deaths and to determine the cause of death; follow-up time was as long as 23 years. Mortality from colorectal cancer among patients with adenomas removed was compared with the expected incidence-based mortality from colorectal cancer in the general population, as estimated from the Surveillance Epidemiology and End Results (SEER) Program, and with the observed mortality from colorectal cancer among patients with nonadenomatous polyps (internal control group).

Results: Among 2602 patients who had adenomas removed during participation in the study, after a median of 15.8 years, 1246 patients had died from any cause and 12 had died from colorectal cancer. Given an estimated 25.4 expected deaths from colorectal cancer in the general population, the standardized incidence-based mortality ratio was 0.47 (95% confidence interval [CI], 0.26 to 0.80) with colonoscopic polypectomy, suggesting a 53% reduction in mortality. Mortality from colorectal cancer was similar among patients with adenomas and those with nonadenomatous polyps during the first 10 years after polypectomy (relative risk, 1.2; 95% CI, 0.1 to 10.6).

Conclusions: These findings support the hypothesis that colonoscopic removal of adenomatous polyps prevents death from colorectal cancer. (Funded by the National Cancer Institute and others.).

Figure 1. Study Enrollment

Of the 9112 patients referred for this study, 2602 with adenomatous polyps and 773 with only nonadenomatous polyps were included in the analysis. Diagnosis was made according to pathological classification at the clinical center. Only patients who provided sufficient demographic information (at least first and last names and either Social Security number or the month and year of birth) were matched against data from the National Death Index. These identifiers were not retained for patients with no polyps or with gross cancer; consequently, none of these patients were included in the analysis of mortality. In addition, 30 patients with adenomas and 3 with nonadenomas did not have sufficient demographic information and were not included in the analysis.

Figure 2. Cumulative Mortality from Colorectal Cancer in the General Population, as Compared with the Adenoma and Nonadenoma Cohorts

We censored the curves at 20 years; the 12th death in the adenoma cohort was at 22 years and was included in the analysis. The numbers of deaths from colorectal cancer are given at the end of the curves for the general population (25.4 expected deaths) and the adenoma cohort (12 observed deaths). Expected deaths are based on data from Surveillance, Epidemiology, and End Results registries in nine areas (SEER9).