Enhancing crossover trial design for rare diseases: Limiting ineffective exposure and increasing study power by enabling patient choice to escape early

The results of the FMF trial and simulation studies suggest that allowing early escape in crossover trial enhanced the design by minimizing patient's exposure to the ineffective treatment arm while maintaining a reasonable study power, which is particularly important for rare disease trials. Choice between the two types of early escape presents tradeoff between study power and exposure to ineffective treatment.