Colonoscopy screening and removal of adenomatous polyps reduced the risk of colorectal cancer death by 53% in a recent study reported in the New England Journal of Medicine (2012;366:687-696).
According to the authors, the findings demonstrate that adenomas identified and removed at colon oscopy are clinically important, because they have the potential to develop into carcinomas. Colorectal cancer is common, with an expected 143,000 new cases and 51,000 deaths due to colorectal cancer in the United States this year. Although polypectomy via colonoscopy has been shown to prevent the development of colorectal cancer, the long-term cancer-specific mortality among people who have had adenomatous polyps removed via colonoscopy is not well studied.
Study subjects (N = 2602) were participants in the National Polyp Study who had adenomatous polyps removed during colonoscopy. The National Polyp Study was a randomized trial of subjects referred for colonoscopy between 1980 and 1990 because of positive findings on a barium enema test, sigmoidoscopy, fecal occult blood tests, or other tests, or because they had symptoms or a family history of colon cancer. Subjects were followed for a median of 16 years, with a maximum follow-up of 23 years.
Among the 2602 patients with adenomas removed during the study, after a median follow-up of 15.8 years, 1246 study subjects (48%) died, including 12 deaths due to colorectal cancer.
Using data from the SEER (Surveillance, Epidemiology, and End Results) registry, the authors determined the expected number of deaths in the general population among people matched for age, sex, and race. The estimated percentage of cumulative deaths from colorectal cancer in the general population over 20 years was 1.5%, compared with a cumulative mortality of 0.8% in the adenoma cohort treated with polypectomy.
The cancer mortality rate of the adenoma cohort was also compared with a group of 773 participants in the National Polyp Study who had been found to have nonadenomatous polyps on initial colonoscopy. Over the first 10 years after the index colonoscopy, the mortality rate was 0.15% in the nonadenomatous polyp group versus 0.19% in those with adenomas.
These findings show that the risk of mortality due to colorectal cancer was similar between patients with adenomas removed at first colonoscopy and those with nonadenomatous polyps removed at that time.
The authors used a model to estimate mortality if the adenomas had not been removed and no intervention had interfered with the natural history of adenomas developing into carcinoma.
“The model showed an even larger reduction in mortality [after] polypectomy than the comparison with the SEER incidence-based mortality rates,” noted lead author Ann Zauber, PhD, Memorial Sloan-Kettering Cancer Center, New York City.
For colonoscopy to be effective, adults who are candidates must comply with screening guidelines. But several studies have shown poor compliance in the United States, as well as a general reluctance to undergo colonoscopy. The compliance problem is not limited to the US. In the same issue of the New England Journal of Medicine, a study from Spain found that only 24.6% of adults offered colonoscopy agreed to undergo the test.