BACKGROUND: Daratumumab has been approved in the United States (US) for patients with multiple myeloma (MM). In the POLLUX clinical trial of MM patients who had received at least one prior line of therapy, patients receiving daratumumab plus lenalidomide plus dexamethasone (DRd) showed significant improvements in efficacy compared to patients receiving lenalidomide plus dexamethasone (Rd) (Dimopoulos et al., NEJM, 2016). However, limited information is available on the cost-effectiveness of DRd. A decision-analytic model was developed to consider direct medical costs from a US payer perspective and to explore the cost-effectiveness of DRd versus Rd in previously treated MM and in a subgroup of patients with only one prior line of therapy (first relapse).
METHODS: The model structure took the form of a partitioned survival analysis with three health states: progression-free survival (PFS), progressive disease, and death. A range of parametric survival functions were fitted to patient-level PFS data from the POLLUX trial with (1) selection based on the Akaike and Bayesian information criteria and (2) priority given to the external validity of extrapolations with conservative survival projections. Diagnostic plots were used to assess the validity of the proportional hazards assumption between DRd and Rd. Due to the number of data events and the follow-up time of the trial, overall survival (OS) was not estimated via parametric extrapolation of trial data but rather by its relationship to PFS, based on a retrospective analysis of approximately 23,000 MM patients (Felix et al., BMC Cancer, 2013). Drug costs were taken from wholesale acquisition costs (Red Book, 2017). Dosing information was extracted from the POLLUX trial. Drug-administration cost (Centers for Medicare and Medicaid Services, 2017), health-state costs, subsequent therapy utilization patterns, and utility weights were sourced from published literature. Cost-effectiveness was estimated over a lifetime horizon, with costs and outcomes discounted at 3% per annum. Incremental cost-effectiveness ratios were calculated, specifically the incremental cost per quality-adjusted life-year (QALY) gained and the incremental cost per life-year gained. One-way and probabilistic sensitivity analyses (PSA) were conducted, as well as scenario analyses around parametric curve selection. All analyses were performed for the overall trial population and for the subgroup of patients with a first relapse.
RESULTS: The best-fit, conservative parametric function for all patients was Weibull and for first relapse patients, exponential. All results were presented as discounted values (Table 1). In the overall trial population, the mean PFS was estimated to be 4.12 and 1.84 years for DRd and Rd, respectively. DRd resulted in an average of 4.24 additional life-years (8.43 life-years – 4.19 life-years) and 3.66 additional QALYs (7.12 QALYs – 3.46 QALYs) over Rd. Costs increased for DRd; the majority were related to drug acquisition of daratumumab and to longer time on treatment due to a longer PFS period. Incremental cost-effectiveness ratios in the overall trial population were $153,073 per life-year gained and $177,456 per QALY gained. Overall, survival (life-years), PFS, and QALYs were greater in the first relapse subgroup for both DRd and Rd than in the overall trial population. Mean PFS was estimated to be 5.02 and 2.09 years for DRd and Rd, respectively. DRd resulted in an average of 4.83 additional life-years (9.51 life-years – 4.68 life-years) and 4.17 additional QALYs (8.06 QALYs – 3.89 QALYs) over Rd. Incremental cost-effectiveness ratios in the first relapse subgroup were $165,134 per life-year gained and $190,985 per QALY gained. One-way and scenario analyses indicated the most sensitive parameters to be PFS distribution, the relationship between PFS and OS, discount rates, utility weights, and drug-acquisition costs. PSA was summarized in the form of scatter plots and cost-effectiveness acceptability curves.
CONCLUSION: Based on the range of plausible cost-effectiveness ratio thresholds ($183,000-$264,000 per life-year gained and $109,000-$297,000 per QALY gained) reported in the 2003 cost-effectiveness decision rules for the US (Braithwaite et al., Med Care, 2008), this analysis suggests that DRd is cost-effective compared to Rd in the treatment of previously treated MM. DVd offers a clinically superior and cost-responsible treatment option for previously treated MM.
