[Statistical design and application of clinical trials with small sample sizes for rare diseases].

Due to the limited number of cases, conducting large-scale clinical trials for rare diseases is challenging. This review introduces several small sample statistical designs tailored for rare diseases, including crossover design, -of-1 design, randomized placebo-phase design, randomized withdrawal design, group sequential design, and adaptive design. It discusses the advantages, disadvantages, and application scenarios of these designs. Additionally, it explores the benefits of Bayes decision-making in clinical trials for rare diseases. The aim is to provide a reference for designing and implementing small sample clinical trials for rare diseases.