Late-starter sites in randomized controlled trials

In a cohort of 14 randomized controlled trials conducted by the Adult AIDS Clinical Trials Group between 1986 and 1999 with a target sample size of >400 (total enrollment 15,531 patients), we evaluated whether "late-starter" sites can make a meaningful contribution to eventual trial accrual. The sites that started recruiting within 5 months from the time the first patient entered the trial were eventually responsible for over 90% of the total enrollment in 11 of the 14 trials. Across the 14 trials some sites, were consistently among the first to start enrollment whereas others were routinely among the last. The late-starter sites are unlikely to make important contributions to eventual trial enrollment in large clinical trials conducted by groups with a fixed number of sites. Protracting administrative efforts to add more sites many months after a multicenter trial has started may not be useful to trial accrual. (C) 2003 Elsevier Inc. All rights reserved.