Nonadvanced colon adenoma may not increase colorectal cancer risk

Reference

Click B, Pinsky PF, Hickey T, Doroudi M, Schoen RE. Association of colonoscopy adenoma findings with long-term colorectal cancer incidence. JAMA 2018;319(19):2021-2031.

Synopsis

These investigators reported follow-up data on 15,935 adults, aged 55 to 74 years, initially enrolled in a randomized trial of flexible sigmoidoscopy screening who had a positive result for polyp or mass and who underwent follow-up with a diagnostic colonoscopy. Lesions detected at colonoscopy were categorized as (1) advanced adenoma (any adenoma greater than or equal to 1 cm, high-grade dysplasia, or with tubulovillous or villous histology); (2) nonadvanced adenoma (adenomas less than 1 cm without advanced histology); or (3) no adenoma. Individuals who assessed outcomes remained masked to study group categorization. A median follow-up of 12.9 years occurred for approximately 90% of participants. The initial colonoscopy identified 2882 patients (18.1%) with advanced adenoma, 5068 (31.8%) with nonadvanced adenoma, and 7985 (50.1%) with no adenoma. Among these patients, the cumulative incidence of CRC over 15 years was 2.9% (95% CI 2.3% - 3.7%) in the advanced adenoma group, 1.4% (1.1% to 1.8%) in the nonadvanced adenoma group, and 1.2% (1.0% to 1.6%) in the no adenoma group. The absolute difference in CRC incidence rate was significantly increased for advanced adenoma versus nonadvanced and no adenoma (1.5% and 1.7%, respectively). However, there was no significant difference in CRC incidence rate for nonadvanced adenoma versus no adenoma. There was also no significant difference in the risk of CRC within the nonadvanced adenoma group in patients with 3 or more polyps compared with those with 1 or 2 polyps. Similarly, the risk of CRC death was significantly increased only among patients initially detected with advanced adenoma when compared with those with no adenoma.