Background: Gemtuzumab ozogamicin (GO) combined with standard of care (SOC) chemotherapy (daunorubicin and cytarabine) is approved for the treatment of patients age 15 years and above with previously untreated, de novo CD33-positive acute myeloid leukaemia (AML). The approval is based on data from the phase III ALFA 0701 trial of GO+SOC vs SOC in this population and excludes acute promyelocytic leukaemia (APL).
Aims: Our study aimed to assess the cost-effectiveness of GO+SOC vs SOC alone for the treatment of de novo AML patients with a Spanish National Health Service perspective.
Methods: A cohort state-transition model, using monthly cycles, was used to estimate the lifetime accumulated cost and benefits in terms of quality-adjusted-life-years (QALYs) in a hypothetical cohort of AML patients with favorable, intermediate and unknown cytogenetic profiles. Long-term relapse-free and overall survival trial data for GO+SOC vs SOC were used to generate individual transitions in the lifetime model. The model represented the disease evolution and included 12 health states: induction therapy, complete remission (CR) or complete remission with incomplete platelet recovery (CRp) (consolidation therapy), CR or CRp (off treatment), relapse (salvage therapy), relapse (noncurative therapy), refractory (salvage therapy), refractory (noncurative therapy), hematopoietic stem-cell transplant (HSCT) procedure, post-HSCT CR or CRp [without graft versus host disease (GVHD)], post-HSCT CR or CRp (with GVHD), functionally cured (off treatment) and dead (Figure 1). Patient profile was defined based on characteristics of the patients included in ALFA 0701 trial, in which there were included patients between 50-70 years old, with de novo AML (except APL) non previously treated and candidates to receive an intensive chemotherapy. Therapeutic regimens were defined based on local practice by an expert panel of 5 hematologist. The SOC chemotherapy was assumed to be idarubicin and cytarabine, the combination most used in Spain based on the expert consensus. QALYs were estimated by applying utility weights for the time spent by the modelled cohort in each health state, and utility decrements associated with adverse events (AE). Total cost estimation (€, 2019 cost year) included drug-acquisition costs (ex-factory price with mandatory deduction applied), HSCT cost, disease management costs per health state, AE management costs and end-of-life costs. Unit costs were obtained from local cost databases and utility data were taken from the literature. All parameters for healthcare resource consumption were validated and agreed by an expert panel. An annual discount rate (3%) was applied for both, cost and health outcomes. Probabilistic sensitivity analyses (PSA) were performed to test model robustness.
Results: In the base-case analysis, higher cost/patient (€183,141 vs €157,676) and greater QALYs (5,70 vs 4,62) gained were obtained with GO+SOC vs SOC. The incremental cost-utility ratio (ICUR) was €23,539/QALY gained. Higher costs of GO+SOC were mainly attributable to drug acquisition; cost savings were seen from relapse prevention and fewer HSCTs. The mean probabilistic ICUR from 1,000 Montecarlo iterations for the PSA was €25,492 per QALY gained (95% CI: €23,564 - €27,733).
Conclusion: Increased costs of adding GO to SOC were offset by improved outcomes. GO added to idarubicin and cytarabine appears as a cost-effective option for the treatment of AML patients; the ICUR obtained is below the most widely accepted willingness-to-pay threshold in Spain (€10,000-30,000/QALYs).
