Effect of statin use on long-term survival after diagnosis of colorectal cancer: Emulating hypothetical target trials using a nationwide real-world database.

82 Background: Observational studies suggest that statin use after colorectal cancer (CRC) diagnosis is associated with improved survival. However, potential bias due to misalignment of time zero in observational studies may distort associations and therefore requires validation using robust epidemiological methods. We aimed to emulate a hypothetical randomized trial—a target trial—for estimating per-protocol effects of statin initiation in patients with incident colorectal cancer on long-term survival. Methods: To emulate a target trial using real-world data, we extracted information from 103,005 patients diagnosed with CRC between 2005 and 2015 from the Korean National Health Insurance (KNHI) database, encompassing health records for the entire Korean population. We excluded individuals who had been prescribed statins for at least 180 days before the CRC diagnosis or those with missing or incomplete demographic information. We set a 180-day grace period and compared the group that initiated statin treatment within 180 days after the CRC diagnosis with the non-statin group using the “clone-censor-weight” method. Patients' demographic and socioeconomic information, along with colorectal cancer treatment, were included as baseline covariates. Additionally, the Charlson Comorbidity Index (CCI) score was included both as a baseline covariate and as a time-varying covariate. Hazard ratios (HRs) for all-cause mortality and CRC-specific mortality within 60 months of baseline were calculated using pooled logistic regression models. Results: Among the 103,005 patients diagnosed with CRC, 88,516 were finally analyzed after the exclusion process. A total of 2,071 (2.3%) individuals initiated statin treatment during the grace period and 86,445 (97.7%) patients did not. Statin initiators, compared with statin noninitiators tended to be older (mean age: 65.7 vs. 62.6) and had a higher CCI score at baseline (mean CCI score: 1.38 vs.1.26). Individuals who initiated statin treatment did not reduce the hazard of all-cause mortality (The adjusted HR 1.01, 95% CI 0.98-1.04) and CRC-specific mortality (The adjusted HR 1.01, 95% CI 0.97-1.04). Conclusions: The results of the analysis after removing potential biases showed that statin was not related to improving survival in CRC patients. The study results conflict with those of previous observational studies but are consistent with the findings of other recently conducted target trial emulations.