Cost-effectiveness of zoledronic acid compared with clodronate in multiple myeloma.

BACKGROUND: In the U.K. Medical Research Council Myeloma IX trial (mmix), zoledronic acid 4 mg once every 3-4 weeks, compared with clodronate 1600 mg daily, reduced the incidence of skeletal related events (sres), increased progression-free survival (pfs), and prolonged overall survival (os) in 1970 patients with newly-diagnosed multiple myeloma. The incidence of confirmed osteonecrosis of the jaw was higher with zoledronic acid than with clodronate. The objective of the present study was to evaluate, based on the findings in mmix, the cost-effectiveness of zoledronic acid compared with clodronate in patients with newly-diagnosed multiple myeloma.

METHODS: An economic model was used to project pfs, os, the incidence of sres and adverse events, and expected lifetime health care costs for patients with newly diagnosed multiple myeloma who are alternatively assumed to receive zoledronic acid or clodronate. The incremental cost-effectiveness ratio (icer) of zoledronic acid compared with clodronate was calculated as the ratio of the difference in cost to the difference in quality-adjusted life years (qalys). Model inputs were based on results of mmix and published sources. Results were generated under different assumptions regarding the beneficial effects of zoledronic acid on os beyond 5 years after treatment initiation.

RESULTS: Assuming lifetime treatment effects of zoledronic acid, treatment with zoledronic acid (compared with clodronate) increased qalys by 0.27 at an additional cost of CA$13,407, yielding an icer of CA$49,829 per qaly gained. If the threshold icer is CA$100,000 per qaly, the estimated probability that zoledronic acid is cost-effective is 80%. Assuming that the benefits of zoledronic acid on pfs and os diminish over 5 years beginning at the end of year 5, the icer is CAN$63,027 per qaly gained. If the benefits of zoledronic acid on pfs and os are assumed to persist for 5 years only, the icer is CAN$76,948 per qaly gained.

CONCLUSIONS: Compared with clodronate, zoledronic acid represents a cost-effective treatment alternative in patients with multiple myeloma.