P37 The Cure Myth: Experience from Recent Health Technology Assessment (HTA) Submissions in Relapsed/Refractory Diffuse Large B-Cell Lymphoma (R/R DLBCL)

Abstract

Recent clinical trials testing novel cancer therapies such as CAR-Ts are detecting a plateau in the survival curves, conveying a potential opportunity for cure. Long-term survival data are limited, and clinicians are often cautious to make conclusions on the basis of the trial outcomes. Nevertheless, cure assumptions have appeared in oncology HTA submissions such as those in R/R DLBCL. This study aims to investigate how cure assumptions are applied across different HTA submissions for therapies in R/R DLBCL. Publicly available HTA dossiers in R/R DLBCL submitted to NICE, SMC, CADTH, ICER, PBAC and HAS in the past five years were reviewed. Information related to cure assumptions (methodology, cure time point, cure proportion) and the critiques received by the HTA bodies were reviewed and extracted. Of the twelve HTA documents identified, ten submissions applied cure assumption in overall survival extrapolation. These submissions focused on two CAR-T agents (axicabtagene and tisagenlecleucel) and polatuzumab vedotin. From the ten submissions that reported cure assumptions, six used cure-mixture models and four used simple cure assumptions. Eight models set mortality of cured patients to that of the general population, while two considered an adjustment factor. Cure was considered only for the intervention arm in seven models, while the rest considered it for all treatments. The timepoint and proportion of cure varied across the submissions. Critiques were mainly around the issues caused by immaturity of survival data, such as uncertainty in cure assumptions and the choice of cure timepoint. While cure modelling is frequently used in R/R DLBCL and in oncology, there seems to be no consensus on the implication of cure and its implementation in the economic analyses. Clear guidance must be provided by health authorities on how to approach the cure concept in economic modelling and how to validate the assumptions.