Resist the Temptation of Response-Adaptive Randomization.

Area of Science:

• Clinical Trials Methodology
• Biostatistics
• Medical Research Ethics

Background:

• Response-adaptive randomization (RAR) is increasingly adopted in clinical trials with the goal of optimizing patient allocation to superior treatments.
• This adaptive approach seeks to enhance trial efficiency and ethical considerations by minimizing exposure to less effective interventions.

Purpose of the Study:

• To critically evaluate the practical implications and statistical validity of response-adaptive randomization in clinical trial design.
• To identify and delineate the inherent challenges and potential pitfalls associated with implementing RAR.

Main Methods:

• The study reviews the statistical and operational consequences of RAR, analyzing its impact on key trial parameters.
• It examines issues such as temporal trends, treatment effect estimation, sample size distribution, and data analysis validity.

Main Results:

• RAR introduces significant biases, including those from temporal trends and potential selection bias due to unblinding.
• It can lead to inefficient treatment effect estimation and volatile sample-size distributions, paradoxically assigning more patients to inferior arms.
• The analytical complexities and potential for bias are particularly pronounced in long-duration platform trials and infectious disease settings.

Conclusions:

• Response-adaptive randomization poses substantial risks that can undermine the fundamental benefits of traditional randomization.
• The identified problems, especially bias and analytical difficulties, suggest that RAR's use should be discouraged in clinical research.
• RAR may negate the core advantages of randomization, a cornerstone of reliable clinical trial evidence.