A recent study from Sweden found no harm in extending the interval for repeat colonoscopy from 10 to 15 years in people who had negative findings on an index exam and do not have a family history of colorectal cancer.
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In the study of nearly 2 million individuals from the nationwide registry, only two CRC cases and one CRC-specific death occurred in the group with a second colonoscopy at 15 years instead of 10; the extended interval potentially avoided 1,000 colonoscopies (JAMA Oncol 2024;10[7]:866-873). The study also reaffirmed the benefit of colonoscopy over no colonoscopy.
The exposed group included patients who had undergone a first colonoscopy when they were between 45 and 69 years of age, with negative findings, defined as no colorectal polyp, adenoma, carcinoma in situ, or CRC before or within six months of screening. The control group included people without colonoscopy who were matched 18:1 by sex, birth year and baseline age (the age of their matched exposed individual at first colonoscopy), yielding 110,074 patients in the exposed group and 1,981,332 in the control group.
During up to 29 years of follow-up after an index colonoscopy with negative findings, 484 incident CRCs and 112 CRC-specific deaths occurred in the exposed group and 21,778 CRC cases and 5,521 CRC-specific deaths occurred in the control group. The 10-year standardized incidence ratio (SIR) and standardized mortality ratio (SMR) were calculated to compare risk for CRC and CRC-specific deaths in the exposed and control groups based on different follow-up screening intervals.
For 15 years after the first negative colonoscopy, the risk for CRC and CRC-specific deaths in the exposed group were significantly lower than those in their matched controls. In that group, the SIR was 0.72 (95% CI, 0.54-0.94) and SMR was 0.55 (95% CI, 0.29-0.94). The exposed group had a cumulative risk for CRC in year 15 that was 72% less than that in the control group.
Extended Interval Not Associated With Increased CRC Cases
The 15-year interval did not greatly increase the number of incident CRC cases. The five-year cumulative incidence rates of CRC (cumulative from years 11-15) in those who had a 10-year repeat colonoscopy and those who did not were 2.9 and 5.3 per 1,000 individuals, respectively, showing that only 2.4 more CRC cases per 1,000 people could be missed by extending the interval after negative index colonoscopy to 15 years.
However, intervals longer than 15 years did not show the same effect. If longer colonoscopy intervals were considered, the number of additional CRC diagnoses gradually increased, with 1.4 extra CRC deaths per 1,000 individuals occurring when a 16- to 20-year interval was used compared with those associated with a 10-year interval, and more CRC diagnoses occurring when the interval was extended further.
Rajesh N. Keswani, MD, MS, the director of endoscopy at Northwestern Memorial Hospital and the director of quality for the Digestive Health Center at Northwestern Medicine, in Chicago, said the study “expands upon prior work showing that a normal high-quality colonoscopy is protective for an extended period in otherwise low-risk individuals. While this evidence would support lengthening intervals further, I would continue to recommend following existing guidelines that recommend a repeat colonoscopy in 10 years.”