Critical review of the quality and development of randomized clinical trials (RCTs) and their influence on the treatment of advanced epithelial ovarian cancer.

Trials on chemotherapy of advanced ovarian cancer published between 1975-88 were systematically reviewed for quality (according to the method of Chalmers) and consistency of tested hypotheses with a view to a meta-analysis of all published studies in the field. Median overall, internal and external validity scores were 47%, 43% and 53%, respectively. No association was found between scores and key features of trials, such as percentage studies with significant results in response or survival or percentage studies with high or low follow-up retention (withdrawal rates less than or greater than or equal to 15%). Only 21% of trials reported a fully blind randomization procedure and only in 13% were drop-outs accounted for by the intent-to-treat method. Only 4 trials entered more than 150 patients per arm, a sample size consistent with detection of an absolute difference of 11% in mortality. The majority of trials (58%) investigated the role of combination regimens versus a single-agent control arm. The remaining trials tested different polychemotherapies. However, within these two general issues, treatment options were quite heterogeneous: seven subgroups were identified by whether cisplatin was present in either the treatment or the control arm. We conclude that the internal coherence and development of randomized clinical trials in advanced ovarian cancer and their methodologic soundness are quite poor. In this situation meta-analysis cannot go beyond a systematic attempt to answer a very general "treatment effectiveness" question.