5-year colonoscopy interval shows noninferiority to 3-year interval for colorectal cancer incidenceTrial shows longer gaps between colonoscopies may be safe for some

This randomized controlled trial was conducted across eight European countries to evaluate the safety and efficacy of different colonoscopy surveillance intervals for patients with high-risk adenomas. The study population included 10,799 patients identified as having high-risk adenomas, defined as having at least 1 adenoma with a diameter of 10 mm or greater, high-grade dysplasia, or villous growth, or having 3 to 10 adenomas of any kind. The study design was a noninferiority trial aimed at determining the optimal interval for follow-up colonoscopy after polyp removal.

The study compared two specific intervention protocols: a first colonoscopy at 5 years after polyp removal versus a first colonoscopy at 3 years after polyp removal. The primary outcome measure was the cumulative incidence of colorectal cancer at 10 years. However, as this is an interim analysis, the follow-up period at the time of reporting was 5.5 years.

Regarding the primary outcome, the 5-year cumulative incidence of colorectal cancer was 0.77% in the 5-year group compared to 0.82% in the 3-year group. This represents a difference of -0.05 percentage points. The trial was designed as a noninferiority study, and the results met this criteria, as the upper boundary of the 99.12% confidence interval was 0.68. In absolute numbers, the 5-year group included 5,398 patients and the 3-year group included 5,401 patients.

Secondary outcomes included the distribution of cancer stage at diagnosis and the number of deaths from colorectal cancer. For deaths from colorectal cancer, the 5-year group recorded 3 (0.06%) deaths, while the 3-year group recorded 2 (0.04%) deaths. No specific effect size or p-values were reported for these secondary outcomes.

Safety and tolerability data were not reported in this interim analysis. Specific rates for adverse events, serious adverse events, or study discontinuations were not provided in the available data.

These results contribute to the ongoing discussion regarding the optimization of colonoscopy surveillance intervals. While the 5-year interval was shown to be noninferior to the 3-year interval at the 5-year mark, it is important to note that the 10-year primary endpoint has not been reached for final analysis.

Methodological limitations include the fact that this is an interim analysis of a trial designed for a 10-year follow-up. Because the 10-year primary endpoint has not been reached, the long-term implications of extending the interval are not yet fully established.

Clinically, these findings suggest that for patients with high-risk adenomas, a 5-year follow-up interval may be a viable alternative to a 3-year interval without increasing the risk of colorectal cancer at the 5-year mark. However, clinicians should interpret these results with caution due to the interim nature of the data.

Questions remain regarding the long-term outcomes beyond the 5-year mark and the specific impact on cancer stage at diagnosis, as the full data set for these secondary outcomes is not yet complete. The trial was funded by the Research Council of Norway and others, and is registered as EPoS II ClinicalTrials.gov number, NCT02319928.