Event-Driven Trial Design

Event-driven trial designs terminate study follow-up upon occurrence of pre-specified clinical events including disease progression, hospitalisation, or death rather than fixed calendar timepoints. This design reduces trial duration and cost particularly for diseases with variable progression rates. Interim efficacy analyses conducted upon predetermined event accumulation enable early trial termination if efficacy thresholds are met. Conditional statistical power increases with event-driven designs relative to time-fixed designs for equivalent information content.

Sample size calculations determine event numbers required for specified statistical power and significance levels. Heterogeneous event rates across trial sites necessitate recruitment flexibility ensuring adequate event accumulation. Blinded interim analyses maintain trial integrity preventing bias from unmasked efficacy data. Stopping rules define event number thresholds triggering trial termination for efficacy, futility, or safety concerns. Regulatory acceptance of event-driven designs has increased as statistical sophistication improves. Adaptive event-driven designs permit interim event rate assessment with protocol modifications optimising information acquisition.