Platform trials offer a framework to study multiple interventions in a single trial with the opportunity of opening and closing arms. The use of a common control in platform trials can increase efficiency as compared to individual control arms or separate trials per treatment. However, the need for multiplicity adjustment as a consequence of common controls is currently a controversial debate among researchers, pharmaceutical companies, as well as regulators. We investigate the impact of a common control arm in platform trials on the type one error and power in comparison to what would have been obtained with a platform trial with individual control arms in a simulation study. Furthermore, we evaluate the impact on power in case multiplicity adjustment is required in a platform trial. In both study designs, the family-wise error rate (FWER) is inflated compared to a standard, two-armed randomized controlled trial when no multiplicity adjustment is applied. In case of a common control, the FWER inflation is smaller. In most circumstances, a platform trial with a common control is still beneficial in terms of sample size and power after multiplicity adjustment, whereas in some cases, the platform trial with a common control loses the efficiency gain. Therefore, we further discuss the need for adjustment in terms of a family definition or hypotheses dependencies.

翻译：平台试验提供了一种在单一试验中研究多种干预措施的框架，并允许灵活增开或关闭试验组。相较于每个治疗方案设置独立对照组或单独开展试验，在平台试验中使用共同对照组可提高效率。然而，因共同对照组而产生的多重性调整需求，目前仍是研究人员、制药公司及监管机构间存在争议的议题。本研究通过模拟实验，比较了采用共同对照组的平台试验与采用独立对照组的平台试验在第一类错误和统计效能上的差异。此外，我们还评估了平台试验在需要多重性调整时对统计效能的影响。研究发现，在两种试验设计中，若不进行多重性调整，家族错误率（FWER）均高于标准双臂随机对照试验；但采用共同对照组时FWER膨胀程度较小。多数情况下，经过多重性调整后，采用共同对照组的平台试验在样本量和统计效能方面仍具优势，但部分场景下其效率增益会消失。因此，我们进一步从家族定义或假设依赖性的角度探讨了调整的必要性。