Policies for study monitoring and interim reporting of results.

Interim analyses of comparative trials are necessary in order to monitor for extreme therapeutic results. However, closing studies and reporting results whenever "trends" appear increases the probability of a false conclusion to well over the desired .05 level. Guidelines for early stopping of comparative trials must be carefully defined to avoid this problem. In addition, to avoid inappropriate early closure of studies due to declining accrual (as investigators draw their own conclusions from early unreliable data), it is recommended that access to interim data be limited to a multidisciplinary monitoring committee responsible for (1) performing and reviewing interim analyses, and (2) deciding when early termination should be considered. Accrual and reporting of studies from two clinical trials groups, one with a policy of limited access to interim data and one without, are compared. The group without monitoring committees had a higher incidence of accrual and reporting problems than the group with monitoring committees.