Background: Trastuzumab has a large financial impact on the average cost of breast cancer treatment. This study reassessed the cost-effectiveness of listing the drug on the subsidised Australian Pharmaceutical Benefits Scheme.
Methods: Using a continuous-time, discrete-event microsimulation model, we examined the effect of 1-year trastuzumab on the total number of disability-adjusted life-years (DALYs) averted among Australian women with human epidermal growth factor receptor-2 (HER2) positive early breast cancer. Target population was women aged 30–100 years and newly diagnosed with the disease in 2003. The model adjusted for tumour size and followed the women up until death or age 100 years. Uncertainty was examined in univariate and probabilistic multivariate sensitivity analyses.
Results: The incremental cost-effectiveness ratio (ICER) was A$132,537 (95% confidence interval 91,172–200,485) per DALY averted. Results were sensitive to restriction of trastuzumab to high-risk (large tumour) and/or high-benefit (young) patients. Suitable combinations of tumour size and age restrictions would improve the cost-effectiveness of trastuzumab. Specifically, restricting trastuzumab to women aged 40 years or younger with tumour sizes 40+ mm reduced the ICER to A$35,290 per DALY averted.
Conclusion: Trastuzumab for HER2-positive early breast cancer had a high ICER. It is unclear why the Pharmaceutical Benefits Scheme listing does not use restrictions to improve the cost-effectiveness of the drug.