Further evidence indicates screening colonoscopy reduces mortality and may detect more adenomas than fecal occult blood testing

Two new studies provided evidence of colonoscopy's effectiveness at detecting cancer and reducing mortality.

The first study included 2,602 patients who had adenomas removed during colonoscopy between 1980 and 1990. In the median 15-year follow up, 1,246 patients died of any cause and 12 of colorectal cancer. Researchers compared those findings to expected rates of colon cancer mortality in the general population and found that about half as many polypectomy patients died than would be expected (incidence-based mortality ratio, 0.47; 95% CI, 0.26 to 0.80). Patients with adenomas and patients with nonadenomatous polyps had similar mortality rates, although with a large confidence interval (relative risk, 1.2; 95% CI, 0.1 to 10.6).

The study authors noted that the results may underestimate the effect of colonoscopy, because they used data from the general population and patients with adenomas are at higher risk. However, the study also included only well-trained gastroenterologists and thus may not be generalizable in the community. Still, the authors concluded that the results support current recommendations for screening colonoscopy.

The second study compared colonoscopy and fecal immunochemical testing (FIT) in a randomized trial of more than 50,000 asymptomatic Spanish adults ages 50 to 69. Participants were invited to one colonoscopy or FIT every two years. According to interim results (including only the first FIT), participation was higher in the FIT group than the colonoscopy group (34.2% vs. 24.6%, P<0.001). Colorectal cancer was found at similar rates in both groups (0.1%), but advanced adenomas were found in more colonoscopy patients (1.9% vs. 0.9%; odds ratio, 2.3; P<0.001), as were nonadvanced adenomas (4.2% vs. 0.4%; odds ratio, 9.8; P<0.001).

The study authors noted that the primary outcome of their trial is colorectal cancer mortality at 10 years of follow-up. The ongoing nature of the FIT screening, and the greater participation that it attracted, could mean that this method will show improvement in cancer detection and mortality reduction as the years go by, the authors said. On the other hand, colonoscopy may be preventing tumors by detecting adenomas early more effectively than FIT, they said.

An editorial accompanying both studies in the Feb. 23 New England Journal of Medicine concluded that the results support use of colonoscopy. The editorialist suggested education about the actual process of colonoscopy to improve compliance and a triage screening system in which everyone is screened at age 60 and only patients with adenomas receive strict follow-up surveillance.