Bias Adjustment Weakens Statin-CRC Survival Association

A nationwide cohort study published in JAMA Network Open found that starting statin therapy after colorectal cancer (CRC) treatment was associated with only a modest survival difference after methods were used to reduce time-related biases. The absolute difference in CRC-specific survival at 60 months was small and not statistically significant.

Investigators used Korean National Health Insurance Service claims from 2005 through 2015 to identify 88,516 adults aged 30 years or older with newly diagnosed CRC, initial cancer treatment, and no statin prescription during the previous 6 months. They emulated a target trial comparing initiation of any statin within 6 months after first CRC treatment with no initiation during that period. Follow-up continued for up to 60 months; 2,071 patients initiated statins and 86,445 did not.

After adjustment using a clone-censor weight approach, statin initiation was associated with lower CRC-specific mortality (hazard ratio [HR], 0.95; 95% CI, 0.92-0.99). However, the standardized 60-month difference in CRC-specific survival was 1.1 percentage points (95% CI, -0.1 to 2.3), which was not statistically significant. All-cause mortality was also lower but did not reach statistical significance (HR, 0.96; 95% CI, 0.93-1.00); the standardized survival difference was 2.4 percentage points (95% CI, 1.0-3.8).

Conventional analyses that deliberately introduced immortal time bias produced much stronger apparent associations, including HRs of 0.17 for CRC-specific mortality and 0.19 for all-cause mortality. The investigators said this attenuation suggests that previously reported protective associations may partly reflect time-related biases and informative censoring.

The study remained vulnerable to residual confounding. Cancer stage was unavailable and approximated through treatment patterns, the 6-month washout could have misclassified remote former statin users, and statins were evaluated as a class. The authors concluded that posttreatment statin initiation is unlikely to confer a large survival benefit in CRC.

Source: Woo HT, Shin A. Statin initiation and mortality after colorectal cancer treatment. JAMA Netw Open. 2026;9(9):e2633680. doi:10.1001/jamanetworkopen.2026.33680