The value of the aggregate data approach in meta-analysis with time-to-event outcomes

Collecting individual patient data has been described as the 'gold standard ' for undertaking meta-analysis. If studies involve time-to-event outcomes, conducting a meta-analysis based on aggregate data can be problematical. T wo meta-analyses of randomized controlled trials with time-to-event outcome s are used to illustrate the practicality and value of several proposed met hods to obtain summary statistic estimates. In the first example the result s suggest that further effort should be made to find unpublished trials. In the second example the use of aggregate data for trials where no individua l patient data have been supplied allows the totality of evidence to be ass essed and indicates previously unrecognized heterogeneity.