Finding a consensus on time-to-event endpoints definitions in marginal zone lymphoma: A Delphi method

A recent systematic review reported that trials involving patients with marginal zone lymphoma (MZL) show marked heterogeneity both in the choice and definitions of primary and secondary endpoints, thus hampering comparability between trials. The main objective of this study was to reach consensus, through a Delphi process, on the definitions of four time-to-event endpoints in MZL trials, by surveying clinicians and methodologists involved in the conduct of clinical trials including patients with MZL. We polled a panel of leading international experts involved in MZL trials by means of self-administered sequential questionnaires in 2021. Of these 105 experts, 62 responded to the Round 1 questionnaire regarding the definitions of progression-free survival (PFS), event-free survival (EFS), time-to-failure (TTF), and time-to-next-treatment (TTNT). Afterward, we therefore focused the Round 2 and 3 questionnaires among principal investigators, coinvestigators, and trial methodologists. Consensus was reached when there was a >80% agreement on all potential events (11 choices) of each endpoint. Participants in our survey reached consensus on three of the four time-to-event endpoints definitions. Consensus was reached on the definitions of PFS and TTNT after Round 1, of TTF after Round 2, and was not reached for EFS after Round 3. The disagreement concerned the event “treatment discontinuation” in EFS definition. The main interest of our study was to elicit investigator's interest in the importance of consistently defining endpoints in MZL trials and to highlight that composite endpoints should not be encouraged. Fifteen years after the last consensus statement on time-to-event endpoints definitions issued in Lugano (2007), both the review of literature and survey of international investigators agree on the inconsistency of endpoints definitions used within the MZL community. Hopefully, revised standardized definitions of endpoints shall be provided at the upcoming International Conference on Malignant Lymphoma in 2023.