Monitoring clinical trials: issues and controversies regarding confidentiality.

During phase III clinical trials in life-threatening disease settings, it is important to ensure that the Data Monitoring Committee (DMC) has exclusive access to the interim efficacy and safety data generated by the data analysis centre, in order to minimize the risk of widespread prejudgement of unreliable trial results based on limited data. This prejudgement could adversely impact rates of patient accrual, continued adherence to trial regimens and ability to obtain unbiased and complete assessment of trial outcome measures. This also could result in publications of early results that might be very inconsistent with final study data on the benefit-to-risk profile of the study interventions. Circumstances arise only rarely in which unblinding of interim data beyond the DMC would enhance the ability of the trial to provide reliable results. However, to address the ethical imperative to protect the interests of study participants, the DMC itself should have access to unblinded efficacy and safety results. Copyright 2002 John Wiley & Sons, Ltd.