Surveillance colonoscopy at five years after high-risk adenoma removal held against three

Design

randomised noninferiority trial across eight European countries, interim analysis at 5.5 years (EPoS II)

Population

10,799 patients after removal of high-risk adenomas

Primary outcome

cumulative incidence of colorectal cancer (10 years at final analysis; 5 years reported here)

Effect

0.77% with first surveillance at 5 years vs 0.82% at 3 years (difference -0.05 percentage points); upper boundary of the 99.12% CI 0.68 against a 0.7-point margin

EPoS II randomised 10,799 patients across eight European countries who had had high-risk adenomas removed — an adenoma of 10 mm or more, with high-grade dysplasia or villous growth, or three to ten adenomas of any kind — to a first surveillance colonoscopy at five years or at the currently recommended three years. The three-year group also had a colonoscopy at five years.

At an interim analysis after 5.5 years, cumulative colorectal cancer incidence at five years was 0.77% with the longer interval and 0.82% with the shorter one, meeting the prespecified noninferiority criterion. Cancer stage at diagnosis did not appear to differ substantially, and five patients in total died of colorectal cancer across both arms.

For an oncology service the relevance is upstream of the clinic. Post-polypectomy surveillance consumes a large and steadily growing share of colonoscopy capacity, and in systems where a symptomatic patient waits months for a diagnostic list, extending a well-defined surveillance interval by two years releases exactly the capacity that is scarce.

Two things to hold. This is an interim report of a trial whose primary endpoint is cancer incidence at ten years, and the comparison is five-year-only surveillance against surveillance at both three and five years.

• Apply the definition precisely: adenoma 10 mm or more, high-grade dysplasia, villous growth, or 3 to 10 adenomas
• Do not extend intervals for patients outside that definition or with a hereditary syndrome
• Where local guidelines still say three years, document the discussion rather than changing practice quietly
• Direct the released endoscopy capacity to symptomatic diagnostic lists
• Await the ten-year analysis before treating this as settled

The statistics, in plain English

The noninferiority margin was 0.7 percentage points on the upper boundary of the confidence interval for the between-group difference; the observed upper boundary was 0.68, so the criterion was met with very little room to spare. That interval is a one-sided 99.12% interval, deliberately conservative because this is an interim look, and the final ten-year analysis will use a 95.33% interval to keep the overall type I error at 5%. Inverse probability weighting was used for patients who did not attend their five-year colonoscopy — a statistical correction for missing data, not observed data.

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