Disease-free survival as a surrogate for overall survival in early-stage pancreatic cancer trials: a correlation meta-analysis.

Objective: Disease-free survival (DFS) is frequently used as the primary endpoint in trials of adjuvant and neoadjuvant therapies for early-stage pancreatic cancer (PC), but its validity as a surrogate for overall survival (OS) remains uncertain. This study evaluates the strength and consistency of DFS as a surrogate for OS in early-stage PC trials. Methods and analysis: This systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Trials of early-stage PC involving drug therapy were identified through PubMed, Embase and Cochrane CENTRAL databases, and data on DFS and OS with HR and CIs were extracted. Trial-level surrogacy of DFS for OS was assessed using weighted linear regression, calculating the coefficient of determination (R²) and surrogate threshold effect (STE). Results: 29 trials involving 6777 patients were included. In adjuvant trials, HR of DFS strongly correlated with HR of OS (R²=0.70) at trial-level, with the STE of 0.94 indicating the maximum DFS HR beyond which OS benefit was unlikely. The correlation strength differed between phase III (R²=0.71) versus phase II (R²=0.67) trials. This correlation was stronger in trials including radiation therapy (R²=0.81) and trials in the neoadjuvant setting (R²=0.90). No trial in our study was a registration trial of a new molecule and all involved chemotherapy. Conclusion: Treatment effects on DFS had a strong correlation with treatment effects on OS, making DFS a potential surrogate endpoint for OS in early-stage PC trials of cytotoxic chemotherapies, but its use in registration trials requires careful consideration due to variability across treatment settings and trial designs. PROSPERO registration number: CRD42024595441.