Cancer Incidence and Mortality in Adenoma Cohorts in Northern California Kaiser

Cancer Incidence and Mortality in Adenoma Cohorts in Northern California Kaiser

Douglas K. Rex, MD, FASGE reviewing Lee JK, et al. Gastroenterology 2019 Oct 4.

Databases developed from colonoscopies performed in the Kaiser Permanente Northern California system provided critical proof that lower adenoma detection rates (ADRs) are associated with a higher risk of interval cancer. These investigators now report the risks of colorectal cancer (CRC) and CRC death after colonoscopy in patients with adenomas compared to those with no adenomas.

Patients with poor bowel preparation, sessile serrated polyps, traditional serrated adenomas, and proximal hyperplastic polyps were excluded. Among 64,422 persons with eligible baseline colonoscopies, 71% had no adenomas, 17% had low-risk adenomas, and 11.7% had high-risk adenomas. Incidence rates in all groups rose over time, but at 10 years, the cumulative incidence of CRC was 0.39% in the no-adenoma group, 0.44% in the low-risk group, and 1.24% in the high-risk group. Mortality rates were .07%, .03%, and .55%, respectively. CRC incidence and mortality were not different between the no-adenoma and low-risk adenoma groups. In multivariable analyses, the effects were not modified by age, sex, race, body mass index, nor ADR > vs <25%. At 6 years of follow-up, the cumulative incidence of surveillance colonoscopy was 9.3%, 40.5%, and 60% in the no-adenoma, low-risk adenoma, and high-risk adenoma groups, respectively.

The central message of the study is that patients with no adenomas or low-risk adenomas have similar risks of CRC incidence and mortality and should have similar surveillance intervals. Complicating this message is the higher exposure to surveillance colonoscopy in the low-risk adenoma group, which could have contributed to cancer protection. It’s also difficult to imagine that ADR, which so profoundly influenced interval cancer risk in previous studies from this group, would not substantially allow stratification of absolute cancer risks within the no-adenoma, low-risk adenoma, and high-risk adenoma groups. Without that detail, the story is incomplete.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.

Douglas K. Rex, MD, FASGE


Lee JK, Jensen CD, Levin TR, et al. Long-term risk of colorectal cancer and related death after adenoma removal in a large, community-based population. Gastroenterology 2019 Oct 4. (Epub ahead of print) (

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