Phase 3 trials reveal control arm overperformance may impact treatment effect estimation, suggesting the need for better designs.
Control arm overperformance is common in phase 3 oncology RCTs and is associated with trial outcomes, suggesting an effect on study power. Because overperformance appears to be especially prevalent when OS is the primary end point, the effects of postprogression therapies on OS may be underappreciated. Alternative strategies for designing trials should be considered for reliable estimation of treatment effects.
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Nalin et al. (2026) studied this question.
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