On being the statistician on a Data and Safety Monitoring Board.

Data and Safety Monitoring Boards (DSMBs) are commonly appointed to monitor emerging data from major clinical trials. This paper describes their organization and remit, and their relationship with other trial committees and structures. The operation of formal stopping rules for safety and efficacy by a DSMB is discussed. The duties of a DSMB, from pre-trial planning through to stopping a study are described in detail, with emphasis on the reporting of information to the DSMB and the reporting of conclusions by the DSMB. The issue of blindness is given prominence and the role of the statistician on the DSMB is explored in detail.