Recommendations and definitions for time-to-event endpoints using real-world data in oncology

<h3>Background</h3> Real-world data is increasingly used to assess effectiveness of treatments in patients treated in everyday clinical practice. The aim of this study is to establish definitions for time-to-event endpoints based on real-world data, and to evaluate their applicability to cancer registry data. <h3>Materials and methods</h3> A multidisciplinary panel consisting of seven epidemiologists, one statistician and seven medical specialists with expertise in gastrointestinal oncology was composed to reach consensus on the definitions of time-to-event endpoints. After obtaining the final definitions, the time-to-event endpoints were applied to a population-based cohort of patients with different types of gastrointestinal cancer from the Netherlands Cancer Registry. <h3>Results</h3> For nine time-to-event endpoints, consensus on the definitions was reached: real-world data based (RW) recurrence-free survival, recurrence rate, local recurrence rate, locoregional recurrence rate, distant recurrence rate, progression-free survival, progression rate, treatment failure rate, and overall survival. For RW disease-free survival, no consensus was reached. All time-to-event endpoints appeared suitable for calculation with Netherlands Cancer Registry data for cohorts with follow-up data based on the established definitions, with the exception of RW-treatment failure rate due to the unavailability of cause of death. <h3>Conclusions</h3> This study offers clear definitions for time-to-event endpoints based on RW data which can be applied to cancer registry data. Uniform use of these definitions in future studies will enable better interpretation of results and aid in comparison between studies, but may require additional development when adapted to other countries, cancer types or data sources.