Colonoscopic Polypectomy and Long-Term Prevention of Colorectal Cancer Deaths

Several screening trials have shown an association between detection of early-stage colorectal cancer and a reduction in mortality from colorectal cancer. In the National Polyp Study, early detection and removal of adenomatous polyps reduced the risk of colon cancer. It was unclear, however, whether the cancers prevented by colonoscopic polypectomy in the cohort were those with the potential to progress to cancer and cause death. This study estimated the long-term effect of colonoscopic detection of adenomatous polyps and their removal on mortality from colorectal cancer. The study population included all patients referred for initial colonoscopy at 7 National Polyp Study (NPS) clinical centers between 1980 and 1990 who had adenomatous or only nonadenomatous polyps. The cause of death and the death rate among patients whose adenomatous polyps had been removed were determined using the National Death Index. The mortality rate for colorectal cancer in the cohort among patients who had adenomas removed was compared with the expected incidence-based mortality rate in the general population (estimated from the Surveillance Epidemiology and End Results Program) and with the mortality rate in an internal control group of patients with nonadenomatous polyps. Among 2602 patients who had adenomas removed after a median of 15.8 years, 1246 patients had died from any cause and 12 had died from colorectal cancer as compared with 25.4 expected deaths from the disease in the general population; this corresponded to an estimated 53% reduction in mortality from colorectal cancer (standardized incidence-based mortality ratio, 0.47; 95% confidence interval, 0.26–0.80). During the first 10 years after polypectomy, mortality from colorectal cancer was similar among patients with adenomas and those with nonadenomatous polyps (relative risk, 1.2; 95% confidence interval, 0.1–10.6; P = 1.0). These findings show that colonoscopic polypectomy results in reduced mortality from colorectal cancer. The data demonstrate that the adenomas identified and removed at colonoscopy include those with the potential to progress to cancer and cause death.