A Cost-Effectiveness Framework for Amyotrophic Lateral Sclerosis, Applied to Riluzole

Abstract

Objectives: Reexamine cost-effectiveness of riluzole in the treatment of amyotrophic lateral sclerosis (ALS) in light of recent advances in disease staging and understanding of stage-specific drug effect.

Methods: ALS was staged according to the "fine'til 9" (FT9) staging method. Stage-specific health utilities (EQ-5D, US valuation) were estimated from an institutional cohort, whereas literature informed costs and transition probabilities. Costs at 2018 prices were disaggregated into recurring costs (RCs) and "one-off" transition/"tollgate" costs (TCs). Five- and 10-year horizons starting in stage 1 disease were examined from healthcare sector and societal perspectives using Markov models to evaluate riluzole use, at a threshold of $100 000/quality-adjusted life year (QALY). Probabilistic and deterministic sensitivity analyses were conducted.

Results: Mean EQ-5D utilities for stages 0 to 4 were 0.79, 0.74, 0.63, 0.54, and 0.46, respectively. From the healthcare sector perspective at the 5-year horizon, riluzole use contributed to 0.182 QALY gained at the cost difference of $12 348 ($5403 riluzole cost, $8870 RC and -$1925 TC differences), translating to an incremental cost-effectiveness ratio (ICER) of $67 658/QALY. Transition probability variation contributed considerably to ICER uncertainty (-30.2% to +90.0%). ICER was sensitive to drug price and RCs, whereas higher TCs modestly reduced ICER due to delayed tollgates.

Conclusion: This study provides a framework for health economic studies of ALS treatments using FT9 staging. Prospective stage-specific and disaggregated cost measurement is warranted for accurate future cost-effectiveness analyses. Appropriate separation of TCs from RCs substantially mitigates the high burden of background cost of care on the ICER.

Keywords: EQ-5D; FT9; amyotrophic lateral sclerosis; fixed costs; riluzole; staging.