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Phase II Design — SCE Medical Oncology MCQ

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HardClinical Trials & StatisticsPhase II DesignSCE Medical Oncology

A 55-year-old woman is enrolling in a clinical trial for a novel checkpoint inhibitor. The trial uses a Simon two-stage minimax design. In the first stage, 15 patients are enrolled and 2 responses are needed to proceed to stage 2. Only 1 response is observed. What happens?

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Correct answer: A — Stop for futility because the prespecified first-stage boundary was not crossed

A Simon two-stage design stops for futility when the observed first-stage response count fails to reach the prespecified continuation boundary. Continue to stage two because one response crossed the Bayesian activity boundary: the design states a frequentist Simon boundary of two responses. Continue to stage two after adding the first-stage response to historical controls: historical-control responses are not added to the observed stage-one count. Expand stage one because the minimax design prioritises expected sample size: the prespecified stopping rule is applied rather than revised after data review. Convert to a single-stage design because the first response establishes feasibility: post-hoc conversion invalidates the calibrated type-I and type-II errors.

Reference: Optimal two-stage designs for phase II clinical trials (Published March 1989): https://pubmed.ncbi.nlm.nih.gov/2702835/; GMC good practice in research and consent (Effective April 2024): https://www.gmc-uk.org/professional-standards/the-professional-standards/good-practice-in-research-and-consent/good-practice-in-research