Should adjuvant zoledronic acid be used in early-stage, endocrine-sensitive breast cancer?

Abstract

e17564 Background: Adjuvant zoledronic acid (ZA) appears to improve disease-free survival (DFS) in women with endocrine-sensitive breast cancer and low estrogen levels (LEL) including post-menopausal women, and pre-menopausal women treated with LHRH agonists. ZA, however, is also associated with potential adverse events and incremental drug acquisition costs. An overall assessment of the long-term clinical and economic impacts of adjuvant ZA may therefore help guide the decision to adopt this novel therapeutic option. We examined the incremental quality-adjusted life-years (QALY) and costs per QALY associated with adjuvant endocrine treatment plus ZA relative to endocrine treatment without ZA in women with endocrine-sensitive breast cancer and LEL. Methods: A generic state-transition model was developed to compute cumulative costs, from a Canadian perspective, and QALY associated with and without adjuvant ZA (4 mg IV qM*3→ q3M*8 → q6M*5) over a 25-year horizon for women with endocrine-sensitive breast cancer and LEL. Costs, utilities, DFS and adverse events were derived from relevant clinical trials, the literature and local resources. One-way and probabilistic sensitivity analyses were conducted for key model parameters. Results: Adjuvant ZA was associated with incremental QALY gains of 0.80 and 0.52 and resultant CU estimates of $3,571 and $7,683 per QALY gained in pre- and post-menopausal women, respectively. CU estimates were robust across reasonable uncertainty ranges in all parameters. Conclusions: Adjuvant ZA appears to be associated with long-term QALY gains in women with endocrine-sensitive breast cancer and LEL as well as CU estimates that are well below commonly accepted North American thresholds. The favourable long-term clinical and economic impacts observed in this study further support the use of adjuvant ZA in this setting.