Abstract
BACKGROUND: Randomised Controlled Trials (RCTs) are the gold standard for evaluating treatment effects. However, missing outcomes can threaten the validity of the results. Missing data pose a unique challenge in time-to-event analyses, where the event time may be censored rather than completely missing. Proper handling of missing event times is crucial to ensure unbiased and reliable conclusions in RCTs. This scoping review examines how missing outcomes in time-to-event studies have been addressed in high-impact medical journals and evaluates the implementation and reporting of multiple imputation (MI) techniques in RCTs. METHOD: This scoping review assessed methods for handling missing time-to-event outcomes in RCTs published between 2019 and 2024 in three high-impact medical journals: The New England Journal of Medicine, The Lancet, and The Journal of the American Medical Association. Studies were reviewed to identify whether missing outcome data were present and, if so, which methods were used to handle them. Studies that applied MI were examined in detail to assess how the MI approach was implemented and reported. The review also explored theoretical approaches for imputing censored event times. RESULTS: A total of 834 articles were identified through a PubMed search. After screening, 383 RCTs underwent full-text review. Of these, 354 (92.4%) had no or < 10% missing outcomes without imputation. The remaining 29 studies (7.6%) addressed missing data using statistical approaches: 12 applied MI, 10 used complete case analysis, 6 conducted best-/worst-case sensitivity analyses, and 1 used a propensity score-based method. MI approaches varied, with some studies lacking detailed reporting. CONCLUSION: In RCTs with survival outcomes, properly handling missing event times is essential. This scoping review reveals that, despite the availability of statistical methods, the treatment of missing time-to-event outcomes remains underutilised and often poorly documented. While many studies reported non-administrative censoring, limited information was provided on whether such censoring was informative or non-informative. Additionally, the reporting of MI techniques is frequently insufficient. These findings highlight a critical gap in the handling and reporting of missing outcomes in survival analysis. Strengthening these practices will enhance the reliability and reproducibility of survival analyses in RCTs.