Risk for Metachronous CRC, Mortality in Adenoma Detection at Index Colonoscopy

neoplasm, colorectal neoplasia, adenoma
Investigators aimed to determine the risk for metachronous CRC among patients with no, low-risk, and high-risk adenomas, and the effects of adenoma status on mortality.

Compared with low-risk adenomas, patients with high-risk adenomas detected upon index colonoscopy are at significantly greater risk for metachronous colorectal cancer (CRC) and mortality, according to study results published in Gastroenterology.

A team of investigators conducted a systematic review and meta-analysis to determine the risk for metachronous CRC among patients with no adenomas, low-risk adenomas, and high-risk adenomas, and how adenoma status may affect mortality risks. The incidence of metachronous CRC and CRC-linked mortality was assessed as the primary outcome, after a baseline colonoscopy. Mortality was measured per 10,000 person-years of follow-up.

A total of 12 studies consisting of 510,019 patients were included in the analysis: 366,033 patients had no adenomas, 52,601 patients had low-risk adenomas, 44,780 patients had high-risk adenomas, and 46,605 patients were unable to be categorized. Among the combined studies, the average patient age was 59.2±2.6 years, 55% of patients were men, and the mean durations of follow-up for no adenoma, low-risk, and high-risk adenoma groups were 8.5±3.3 years, 8.4±3.3 years, and 8.8±3.5 years, respectively.

The CRC incidence among patients with no adenomas, low-risk adenomas, and high-risk adenomas was 3.4 per 10,000 person-years, 4.5 per 10,000 person-years, and 13.81 per 10,000 person-years, respectively. Compared with the no adenoma group, the odds ratios (OR) for CRC per 10,000 person-years in the low-risk and high-risk adenoma groups were 1.26 and 2.92, respectively.

Of the 12 studies included, 3 studies reported data on CRC-related mortality in all 3 groups. Among patients in the no adenoma, low-risk adenoma, and high-risk adenoma groups, pooled CRC-related mortality rates per 10,000 person-years were 0.71, 0.78, and 2.07, respectively. Compared with no adenomas, the OR for CRC-related mortality in the low-risk adenoma group and high-risk adenoma group was 1.15 and 2.69, respectively, suggesting a significant association between the detection of high-risk adenomas and CRC-related mortality. 

“We recommend that the interval for follow-up colonoscopy should be the same in patients with [low-risk adenomas] or no adenomas but that the [high-risk adenoma] group should have a more frequent surveillance interval for CRC surveillance compared with these groups,” the investigators noted. “Future studies should evaluate whether surveillance intervals could be lengthened beyond 10 years in the no-adenoma and [low-risk adenoma] groups after an initial high-quality index colonoscopy,” they concluded.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.


Duvvuri A, Chandrasekar VT, Srinivasan S, et al. Risk of colorectal cancer and cancer related mortality after detection of low-risk or high-risk adenomas, compared with no adenoma, at index colonoscopy: a systematic review and meta-analysis. Gastroenterol. 2021;160(6):1986-1996. doi: 10.1053/j.gastro.2021.01.214