Economic Evaluation of Adjuvant Trastuzumab Emtansine in Patients with HER2-Positive Early Breast Cancer and Residual Invasive Disease after Neoadjuvant Taxane and Trastuzumab–Based Treatment in Canada

Background: In the katherine trial, adjuvant trastuzumab emtansine [T-DM1, Kadcyla (Genentech, South San Francisco, CA, U.S.A.)], compared with trastuzumab, significantly reduced the risk of recurrence or death by 50% (unstratified hazard ratio: 0.50; 95% confidence interval: 0.39 to 0.64; p < 0.0001) in patients with HER2-positive early breast cancer (ebc) and residual invasive disease after neoadjuvant systemic treatment. A cost–utility evaluation, with probabilistic analyses, was conducted to examine the incremental cost per quality-adjusted life–year (qaly) gained associated with T-DM1 relative to trastuzumab, given the higher per-cycle cost of T-DM1. Methods: A Markov model comprising a number of health states was used to examine clinical and economic outcomes over a lifetime horizon from the Canadian public payer perspective. Patients entered the model in the invasive disease-free survival (idfs) state, where they received either T-DM1 or trastuzumab. Transition probabilities between the health states were derived from the katherine trial, Canadian life tables, and published literature from other relevant clinical trials (emilia, cleopatra, and M77001). Resource use, costs, and utilities were derived from katherine, other clinical trials, published literature, provincial fee schedules, and clinical expert opinion. Sensitivity analyses were conducted for key assumptions and model parameters. Results: Compared with trastuzumab, adjuvant T-DM1 was associated with a cost savings of $8,300 per patient and a 2.16 incremental qaly gain; thus T-DM1 dominated trastuzumab. Scenario analyses yielded similar results, with T-DM1 dominating trastuzumab or producing highly favourable incremental cost–utility ratios of less than $10,000 per qaly. Conclusions: Adjuvant T-DM1 monotherapy is a cost-effective strategy compared with trastuzumab alone in the treatment of patients with HER2-positive ebc and residual invasive disease after neoadjuvant systemic treatment.