Cost-effectiveness Analysis of Ado-trastuzumab Emtansine (T-DM1) for the Adjuvant Treatment of Patients With Residual Invasive HER2+ Early Breast Cancer in the United States

Ado-trastuzumab emtansine (T-DM1) was recently approved for patients with human epidermal growth factor receptor 2 positive (HER2+) early breast cancer (eBC) with residual invasive disease after neoadjuvant taxane and trastuzumab-based treatment. Cost-effectiveness analysis was conducted to compare T-DM1 versus trastuzumab in the United States.A Markov cohort-based model tracked clinical and economic outcomes over a lifetime horizon from a US payer perspective. The model included 6 health states: invasive disease-free, nonmetastatic (locoregional) recurrence, remission, first-line and second-line metastatic BC and death. Model state transitions were based on statistical extrapolation of the head-to-head KATHERINE study and published sources. Dosing and treatment duration reflected prescribing information and trials. Costs (2019 US dollars) associated with pharmaceutical treatment (wholesale acquisition costs), health state specific care, adverse events, and end-of-life care were included. Health state utilities were obtained from KATHERINE and published literature.T-DM1 dominated trastuzumab, yielding lower lifetime costs (-$40,271), and higher life-years (2.980) and quality-adjusted life-years (2.336). Results were driven by patients receiving T-DM1 spending less time in more costly downstream health states, as these patients are less likely to experience a recurrence overall, despite having a higher likelihood of metastatic disease (distant recurrence) in the subset of patients who experience recurrence. Probabilistic sensitivity analysis indicated robust results, with 96.7% of 5000 stochastic simulations producing dominance for T-DM1. The most influential variables were related to treatment costs, off treatment utilities, and health state costs. Additional scenario analyses tested a range of model inputs and assumptions, and produced consistent results.Relative to trastuzumab, T-DM1 treatment for patients with HER2+ eBC who have residual invasive disease after neoadjuvant taxane and trastuzumab-based treatment is likely to reduce the overall financial burden of cancer, while simultaneously improving patient outcomes.