Increasing attention has been paid to the risks and benefits of terminating large clinical trials before reaching prespecified targets, because such decisions can greatly affect the implementation of findings. The Department of Veterans Affairs (VA) Cooperative Studies Program (CSP) is a research infrastructure dedicated to conducting high-quality clinical research. A scoping review was performed to characterize barriers preventing the attainment of prespecified recruitment, statistical power, or sample-size targets in VA CSP trials. A trial was eligible for inclusion if the trial was sponsored by the VA CSP, primary findings were published within the last 10 years, and a decision was made to terminate enrollment or follow-up before meeting a priori recruitment or endpoint targets. In 11 of 29 included trials (37.9%), a decision was made to terminate the trial early. The most common reason for early termination was related to under-recruitment (n = 5). Other reasons included early detection of safety signals (n = 2), futility (n = 1), and benefit (n = 1). This review highlights recruitment as a critical facet of trial conduct that may hinder the production of high-quality data and thus warrant additional attention. Solutions to enhance recruitment now implemented by the VA CSP, including dedicated enrollment infrastructure and screening facilitated by informatics approaches, show promise in reducing this cause for early termination.
