Toxicity monitoring is essential in Phase II clinical trials to ensure participant safety. While monitoring rules are well-established for single-arm trials, two-cohort trials present unique challenges because toxicities are expected to be similar between cohorts but may still differ. Current approaches either monitor the two cohorts independently, which ignores their similarity, or pool them together as a single arm, which neglects heterogeneity between cohorts. We propose a Bayesian method based on a bivariate beta prior that provides a compromise between these two approaches. The marginal posterior distribution is derived as a mixture of beta distributions, enabling exact calculations of the proposed method's operating characteristics. Examples demonstrate that joint monitoring offers a balanced approach between the independent and pooled methods. Keywords: Toxicity; Two-cohort; Phase II clinical trial; Monitoring rules; Bivariate Beta; Exact Operating characteristics

翻译：在二期临床试验中，毒性监测对于确保受试者安全至关重要。虽然单臂试验的监测规则已较为成熟，但双队列试验因其队列间毒性预期相似但仍可能存在差异而面临独特挑战。现有方法或独立监测两个队列（忽视其相似性），或将其合并为单臂（忽略队列间异质性）。我们提出一种基于二元贝塔先验的贝叶斯方法，在以上两种方法之间取得平衡。其边缘后验分布被推导为贝塔分布的混合形式，从而可精确计算所提方法的操作特征。实例表明，联合监测在独立法与合并法之间提供了一种均衡方案。关键词：毒性；双队列；二期临床试验；监测规则；二元贝塔；精确操作特征