People who had undergone adenoma removal had a higher risk for colorectal cancer than the general population.

Studies estimating the risk for colorectal cancer in patients who have undergone adenoma removal versus the general population have yielded widely discordant results. These discrepancies can sometimes be explained by variability in patient eligibility requirements, types of follow-up, and source populations.


Now, investigators have conducted a retrospective cohort study to compare the risk for colorectal cancer after adenoma removal with that in the general population. Using population-based data registries, they identified 5779 residents of Burgundy, France, who had undergone a first-time adenoma removal and recorded subsequent cancer diagnoses. Median follow-up time from the date of adenoma diagnosis was 7.7 years.

Results were as follows:

•     Excluding the first year after adenoma removal, more colorectal cancers were diagnosed in the study population than the general population (87 vs. 69; standardized incidence ratio, 1.26).

•     At initial colonoscopy, 33% of patients had advanced adenomas (defined as having size ?1 cm, villous elements, or high-grade dysplasia), and their risk for incident colorectal cancer was higher than in the general population (SIR, 2.2).

•     Among those with nonadvanced adenomas, the risk was lower than that in the general population (SIR, 0.68).

•     Among 4881 patients for whom information on colonoscopy follow-up was available, 58% had ?1 follow-up colonoscopy.

•     Among those with advanced adenomas who did not have follow-up colonoscopy, risk for cancer was four times higher than in the general population (SIR, 4.26); those who did receive follow-up colonoscopy were not at increased risk.

•     Among patients with advanced adenomas, the proportion with advanced-stage cancers was 28.3% in those with colonoscopic follow-up and 7.5% in those without follow-up.

Citation(s):

Cottet V et al. Long-term risk of colorectal cancer after adenoma removal: A population-based cohort study. Gut 2011 Nov 22; [e-pub ahead of print].