Long‐term risk of colorectal cancer after removal of adenomas during screening colonoscopies in a large community‐based population in China

Patients with conventional adenoma removal are recommended to undergo colonoscopy surveillance to prevent colorectal cancer (CRC). However, evidence supporting the guidelines of colonoscopy surveillance is limited, especially among the Chinese population. We investigated the association between colonoscopy adenoma findings and CRC risk among individuals aged 40 to 74 years who underwent baseline colonoscopy from 2007 to 2016 in Jiashan and Haining, Zhejiang, China; 34 382 participants were categorized into advanced adenoma, nonadvanced adenoma and no adenoma based on adenoma findings. A multivariable Cox regression model was used to estimate the hazard ratio (HR) of CRC incidence with adjustment for potential confounding factors. After a median follow-up time of 7.7 years, 113 incident cases of CRC were identified (18 occurred in 1632 participants with advanced adenoma, 16 in 3973 participants with nonadvanced adenoma and 79 in 28 777 participants with no adenoma). Compared to no adenoma group, the adjusted HR for CRC in advanced adenoma group was 4.01 (95% CI, 2.37-6.77). For nonadvanced adenomas, individuals with ≥3 adenomas showed an increased risk of CRC (HR, 3.65; 95% CI, 1.43-9.31), but no significantly increased risk of CRC was found for 1 to 2 nonadvanced adenomas, compared to those with no adenoma. Our study suggested that the risk of subsequent CRC increased in individuals with high-risk adenoma (at least one advanced adenoma or ≥3 nonadvanced adenomas), but not in those with 1 to 2 nonadvanced adenomas. These results provide the first evidence from the Chinese population for the current surveillance guidelines.