RANDOMIZATION PROCEDURES FOR ANALYZING CLINICAL-TRIAL DATA WITH TREATMENT RELATED WITHDRAWALS

The problem of treatment related withdrawals has not been fully addressed in the statistical literature. Statistical procedures which compare efficacies of treatments when withdrawals may occur prior to the conclusion of a study are discussed. A unified test statistic which incorporates all available data, not just the last values and adjusts for withdrawal patterns, proportion of withdrawals, and level of response prior to withdrawal has been developed with the help of data- dependent scoring schemes. A randomization technique has been developed to compute an empirical significance level for each scoring system under both the Fulldata and Endpoint data for a specified parameter configuration. The proposed methods have been applied to a subset (Allen Park Hospital) of the VA study 127.