Modelling the long-term cost-effectiveness of riluzole for the treatment of amyotrophic lateral sclerosis

This study reports the results of a long-term cost-effectiveness analysis of riluzole in the treatment of amyotrophic lateral sclerosis (ALS) in the United Kingdom. The aim was to assess the implications of life extension offered by riluzole in terms of the time spent in each health state which ALS patients experience. The long-term analysis was carried out using a Markov model by extrapolating the transition probabilities derived from clinical trial data. Data for the model came from a cohort of 954 patients drawn from a large randomised, double-blind, placebo-controlled multicentre (France, Belgium, North America, UK, Germany and Spain) trial between December 1992 and December 1994. The results suggest that riluzole is effective in prolonging life and that a larger proportion of patients treated with riluzole will stay longer in states where functional status is least impaired. The additional life expectancy of the intervention over the three-year period suggests that it would be necessary to treat three patients for three years to obtain one additional life-year. Riluzole offsets approximately half of the additional costs of treatment through extending the time that patients spend in the milder, less expensive phases. Therefore, the cost per unadjusted additional life-year gained was estimated as £8,587 over the expected lifetime of ALS patients. The model was estimated over 12 years (survival rate in the riluzole group was less than 1%), which is broadly in line with similar illnesses. Our findings show that although incremental cost figures are not sensitive to the cost of health states, the higher the cost of terminal state the lower the additional cost of life-year saved.