The number of subjects required to detect a therapeutic effect in Corticobasal Degeneration (CBD) depends on several factors, including the expected effect of the therapy, the variability of the outcome measures, the desired statistical power, and the significance level. Generally, studies aiming to detect therapeutic effects in CBD often require a larger sample size due to the rarity and heterogeneity of the disease. For example, a phase 2 trial assessing the efficacy of a novel therapeutic might need to enroll around 50 to 100 subjects per group to detect a moderate effect size, accounting for dropouts and ensuring sufficient power (Boxer, 2017; Höglinger, 2021). In rare diseases like CBD, multi-center collaborations and adaptive trial designs are often employed to maximize recruitment and enhance the study’s power to detect treatment effects.
Sample size analysis performed by Biospective based on the 4RTNI Study data for assessment of progression of MRI brain atrophy in a CBD population over a 12-month period. Graph of sample size per arm for an effect of 20% to 80%, calculated as two-tailed assessment per arm (α = 0.05, β = 0.8).