Commonly used in the fields of oncology, cardiology, and others, time-to-event (TTE) outcomes assess not only the occurrence of an event but the amount of time that has lapsed leading up to its occurrence. For individuals in which the event did not occur, their time under observation is included.
TTE outcomes can provide useful insight into, for instance, into how long individuals survive when taking a new drug for advanced cancer. Statistical methods of calculating TTE outcomes include the use of curves and probabilities (Kaplan-Meier curves) and hazard ratios (HRs).
In addition to being more statistically complex than a simple risk ratio, TTE outcomes are often not reported adequately enough in trials to be used in a meta-analysis without some amount of imputation or exclusion of data, which can introduce error.
In an article published in the July 2023 issue of Journal of Clinical Epidemiology, Goldkuhle and colleagues more closely examined the use of TTE outcomes in meta-analyses included in both Cochrane and non-Cochrane systematic reviews between 2017 and 2020. In the 50 included reviews, a median two TTE outcomes were included in meta-analyses, the most common being comparing the use of biologics and drugs in the treatment of neoplasms.
However, a lack of clear reporting in the 235 trials informing these systematic reviews could easily lead to incomplete data. For instance, only 82% of the trials included a measure of follow-up duration. Information about missing data was only reported for each trial arm in 134 (57%) of the trials, and about one-third of trials reported no information at all in this respect.
The authors conclude that trial authors using TTE outcomes should more stridently follow the Consolidated Standards of Reporting Trials (CONSORT) extension to trial outcomes, while specific guidance is needed for the reporting of meta-analysis of TTE outcomes.
Goldkuhle, M. et al. (2023). Meta-epidemiological review identified variable reporting and handling of time-to-event analyses in publications of trials included in meta-analyses of systematic reviews. J Clin Epidemiol 159: 174-189.
The full-text publication can be accessed here.