Presentation (CTI)

OBJECTIVES: Equal value life-year (evLY) is becoming increasingly popular as a complement to quality-adjusted life-year (QALY) as a measure of health gain to inform medical policy decisions. evLY, like QALY, compares the improvements or decrements in quality of life (QoL) across different interventions. When modelling serious illness or chronic disability, QALY approach often assigns a lower quality of life to the life extensions, thereby undervaluing the benefits of new interventions. evLY overcomes this limitation by assigning a population-based average utility to the life extensions. Work by Campbell and colleagues (2023) demonstrated how to estimate evLY for a two-state (alive and dead) model, but didn’t present a generalizable approach for evLY calculations in any model with more than two states. Our objective for this study is to present an approach for estimating evLY for standard three-state partitioned survival models (PSMs).
METHODS: We developed a hypothetical three-state PSM for two hypothetical drugs. Drug A was assumed to be the current standard of care with 6.1 months of median progression-free survival (PFS) and 12.3 months of median overall survival (OS). Drug B was assumed to be a new intervention with superior median PFS (10.2 months) and median OS (22.3 months). We calculated QALY assuming utility weights of 0.726 for PFS and 0.512 for post-progression survival (PPS). While calculating evLY, 0.851 utility weight was applied to the life extensions. We also modelled a special scenario where PFS for drug B (13.5 months) was higher than OS for drug A (12.3 months).
RESULTS: In the base case, incremental evLY was 0.813 compared to an incremental QALY of 0.530. Under special scenario, incremental evLY was 0.861 compared to an incremental QALY of 0.603.
CONCLUSIONS: evLY could be easily estimated for a three-state PSM using the approach proposed here. More research will be required to generalize evLY calculations for n-state models.