Detection rates of adenomas, advanced adenomas, and colorectal cancers among the opportunistic colonoscopy screening population: a single-center, retrospective study

Background: Colorectal cancer (CRC) screening is effective in reducing CRC incidence and mortality. The aim of this study was to retrospectively determine and compare the detection rate of adenomas, advanced adenomas (AAs) and CRCs, and the number needed to screen (NNS) of individuals in an average-risk Chinese population of different ages and genders.Methods: This was a retrospective study performed at the Institute of Health Management, Chinese People’s Liberation Army General Hospital. Colonoscopy results were analyzed for 53,152 individuals finally enrolled from January 2013 to December 2019. The detection rate of adenomas, AAs, or CRCs was computed and the characteristics between men and women were compared using chi-squared test.Results: The average age was 48.8 years (standard deviation [SD], 8.5 years) for men and 50.0 years (SD, 9.0 years) for women, and the gender rate was 66.27% (35,226)vs. 33.73% (17,926). The detection rates of adenomas, AAs, serrated adenomas, and CRCs were 14.58% (7750), 3.09% (1641), 1.23% (653), and 0.59% (313), respectively. Men were statistically significantly associated with higher detection rates than women in adenomas (17.20% [6058/35,226], 95% confidence interval [CI] 16.74-17.53%vs. 9.44% [1692/17,926], 95% CI 8.94-9.79%,P < 0.001), AAs (3.72% [1309], 95% CI 3.47-3.87%vs. 1.85% [332], 95% CI 1.61-2.00%,P < 0.001), and serrated adenomas (1.56% [548], 95% CI 1.43-1.69%vs. 0.59% [105], 95% CI 0.47-0.70%,P < 0.001). The detection rate of AAs in individuals aged 45 to 49 years was 3.17% (270/8510, 95% CI 2.80-3.55%) in men and 1.69% (69/4091, 95% CI 1.12-1.86%) in women, and their NNS was 31.55 (95% CI 28.17-35.71) in men and 67.11 (95% CI 53.76-89.29) in women. The NNS for AAs in men aged 45 to 49 years was close to that in women aged 65 to 69 years (29.07 [95% CI 21.05-46.73]).Conclusions: The detection rates of adenomas, AAs, and serrated adenomas are high in the asymptomatic population undergoing a physical examination and are associated with gender and age. Our findings will provide important references for effective population-based CRC screening strategies in the future.