Aspirin after completion of standard adjuvant therapy for colorectal cancer (ASCOLT): A systematic review and meta-analysis.

BACKGROUND

Colorectal cancer (CRC) carries a high recurrence risk. Aspirin has been proposed for secondary prevention, but its benefit remains uncertain. This systematic review and meta-analysis evaluated aspirin's impact on disease-free survival (DFS) and overall survival (OS).

METHODS

A systematic search of four databases (PubMed, Embase, Scopus, the Cochrane Library) was conducted from inception to January 2025 using predefined inclusion and exclusion criteria. Screening and data extraction were performed independently. Study quality was assessed using RoB 2 and the Newcastle-Ottawa Scale. Ten studies were included, comprising retrospective cohorts, population-based cohorts, prospective observational analyses, and Phase III randomized controlled trials (RCTs). A random-effects meta-analysis was conducted to pool effect sizes as odds ratios (ORs) with 95% confidence intervals (CIs). Heterogeneity was quantified using I2 and τ2, and sensitivity analyses included leave-one-out testing. All analyses followed PRISMA guidelines.

RESULTS

Ten studies were included. Pooled analyses of observational studies showed no statistically significant improvement in OS (OR 0.92, 95% CI 0.78-1.08) or DFS (OR 0.90, 95% CI 0.74-1.08) among aspirin users. Considerable heterogeneity and inconsistency were observed across studies. RCTs likewise demonstrated no clear survival benefit, with effect estimates close to unity. Safety data were limited and variably reported, precluding firm conclusions regarding adverse outcomes.

CONCLUSION

Current evidence does not support aspirin as adjuvant therapy for secondary prevention in CRC. Future research should target biomarker-defined subgroups for potential benefits.