Background: Breast cancer is the most commonly diagnosed cancer among Australian women, accounting for 28% of all cancer cases in this population. About 20-30% of breast cancer cases are human epidermal growth factor receptor-2 (HER2) positive. One-year adjuvant trastuzumab increases disease-free and overall survival for patients with HER2- positive early breast cancer (EBC). Trastuzumab is subsidised in Australia, but its cost-effectiveness has not yet been well examined in this country.
Objective: To estimate the cost-effectiveness of one-year adjuvant trastuzumab administered every three weeks for Australian women with HER2-positive EBC over a lifetime, relative to standard chemotherapy alone.
Methods: A continuous-time, discrete-event simulation model was developed. A health care sector perspective was used, and thus, only direct medical costs were included. Efficacy data were based on a meta-analysis of clinical trials on adjuvant trastuzumab. Disability weights were derived from the literature. Costs were calculated based on resource utilisation using Australian data. A lifetime horizon was adopted. Outcome measures were life-years (LYs) and health-adjusted life-years (HALYs). Costs and benefits were discounted at 3%. A threshold of A$50,000 per HALY gained was used.
Results: The cost-effectiveness of trastuzumab was estimated to be A$133,155 per HALY gained (A$105,768 per LY gained). It was positively associated with tumour size and inversely associated with age at diagnosis. Results were mainly driven by the drug acquisition cost and discount rate.
Conclusion: Over the lifetime, the addition of one-year adjuvant trastuzumab to standard chemotherapy for Australian women with HER2-positive EBC is not cost-effective compared with standard chemotherapy alone.