OBJECTIVES: In cost-utility analyses (CUAs), health state utility values (HSUVs) are commonly adjusted according to population age to reflect the effect of aging on quality of life (QoL). Recently, Versteegh et al. 2022 reported that time-to-death (TTD) also drives QoL decline. Our objective was to compare the effect of age-based and TTD-based HSUV adjustments in a relapsed and/or refractory multiple myeloma (RRMM) CUA.

METHODS: Among the indications assessed in Versteegh et al., RRMM was selected for the case study. The CUA used a partitioned survival model structure, and clinical and cost parameters obtained from NICE TA897, evaluating daratumumab, bortezomib and dexamethasone (DBd) vs. bortezomib and dexamethasone (Bd). Parametric survival functions were generated from digitized curves of the CASTOR trial and log-logistic distribution was selected as base case and compared to TA897 to ensure consistency. HSUVs were adjusted using age-and sex-based norms and TTD decrements published by Versteegh et al. Sensitivity and scenario analyses were performed to identify when utility adjustment method had the largest impact.

RESULTS: Using the age-based adjustment, total QALYs were 5.233 and 2.110 for DBd and Bd, respectively. Using the TTD-based adjustment, total QALYs of DBd increased to 5.260 and total QALYs of Bd decreased to 1.888. The ICERs of DBd vs. Bd were £78,687/QALY and £72,884/QALY using the age-adjustment and TTD-adjustment approaches, respectively. In all scenarios, incremental QALYs of DBd vs. Bd were higher with TTD adjustments, leading to lower ICERs. When using the optimistic lognormal distribution to extrapolate DBd OS, the difference of incremental QALYs between adjustment approaches was 27.7% larger than the base case. The pessimistic Gompertz function reduced incremental QALYs between approaches.

CONCLUSIONS: In a RRMM case study with a large survival difference between comparators, TTD-based HSUV adjustments increased incremental QALYs compared to age-based adjustments. The difference in incremental QALYs between approaches diminishes as survival benefit diminishes.