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A planned check partway through a trial to see whether the new treatment has any realistic chance of proving better; if not, the trial is stopped to spare patients and money. The opposite rule stops a trial early when benefit is overwhelming.
Independent data monitoring committees review unblinded interim data against pre-specified boundaries: futility boundaries (often a conditional power below 10-20%) end trials such as TrilynX (xevinapant) and a string of phase 3 immunotherapy combinations; efficacy boundaries (O'Brien-Fleming or Lan-DeMets alpha spending) allow early positive readouts, as in KEYNOTE-006 and CheckMate 067. Stopping early for efficacy can overestimate effect size and truncate safety and survival follow-up, while futility stops sacrifice the chance of a late benefit. Sponsors also stop trials for 'business reasons' or poor accrual, which is not the same as futility.
Shares Data monitoring committee (DSMB, IDMC), Accrual and enrolment, Group sequential design, stopping rules and alpha spending, Primary, secondary and co-primary endpoints.
Shares Statistical significance (P values, alpha, multiplicity), Primary, secondary and co-primary endpoints, MAGNITUDE, Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover.
Shares Statistical power, sample size and re-estimation, Primary, secondary and co-primary endpoints, Interim analysis, readout and data cut-off.
Shares Statistical significance (P values, alpha, multiplicity), MAGNITUDE, Why trials fail: underpowered, wrong endpoint, control arm drift, subgroup fishing, crossover.
Shares Response-adaptive randomisation, Statistical power, sample size and re-estimation, Data monitoring committee (DSMB, IDMC), Group sequential design, stopping rules and alpha spending.
Shares Statistical significance (P values, alpha, multiplicity), Group sequential design, stopping rules and alpha spending.
Shares Statistical power, sample size and re-estimation, Data monitoring committee (DSMB, IDMC), Group sequential design, stopping rules and alpha spending, Interim analysis, readout and data cut-off.
Shares Data monitoring committee (DSMB, IDMC), Accrual and enrolment, Interim analysis, readout and data cut-off.