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Underpowered Event-driven Trial — SCE Medical Oncology MCQ

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HardClinical Trials & StatisticsUnderpowered Event-driven TrialSCE Medical Oncology

A phase III overall-survival trial is designed for its final analysis after 500 deaths. At the planned calendar review only 350 deaths have occurred, no unblinded efficacy boundary was prespecified for that time, and safety is acceptable. Which action best preserves the design and type-I-error control?

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Correct answer: E — Continue blinded follow-up to the planned 500-event analysis and retain the prespecified efficacy test

For a time-to-event endpoint, the planned number of events principally determines information and power. An unplanned final test at 350 events changes the design and may be underpowered; post hoc endpoint switching, alpha manipulation or external-control pooling do not preserve the prespecified estimand or error control. Continued follow-up, and only protocol-appropriate blinded design adjustments, retain trial integrity.

Reference: ICH E9 Statistical Principles for Clinical Trials (ICH harmonised guideline): https://database.ich.org/sites/default/files/E9_Guideline.pdf