What discontinued trials teach us about trial registration?

Objective: Trial registries were set up to improve transparency, remove duplication, improve awareness and avoid waste. Many trials never reach the point of patient enrolment due to a myriad of reasons. The aim of this study was to investigate the reasons for and characteristics of discontinuation of trials.

Results: A total of 163 discontinued trials were identified and compared to completed trials. A Survey was designed to further explore the nature and conduct of the trial. No differences in registered and categorised information was observed between discontinued and completed trials. Most trials discontinue due to patient or participant recruitment issues, often related to funding. Substantial changes to procedures or the protocol or changes to recruitment strategy were also commonly cited reasons. Survey information was available for 21 discontinued and 28 completed trials and no obvious differences could be identified. Our findings highlight the underlying problem of lack of detail, suboptimal recording, dated information and incomplete reporting of trials within a trial registry which hampers sharing and learning. To date, important progress has been made by the implementation of standards and the requirement of trials to be registered. Our review identifies areas where further improvements can be made.