OBJECTIVES: To assess the cost-effectiveness of trastuzumab emtansine (T-DM1) versus trastuzumab for the adjuvant treatment of patients with residual invasive HER2-positive breast cancer (BC) after completion of preoperative systemic treatment in the Portuguese setting.

METHODS: The cost-effectiveness analysis was based on a six state Markov model using data from the KATHERINE study, a randomized, multicenter, open-label phase III clinical trial. The model estimated patients’ pathway from invasive disease-free survival (iDFS) through non-metastatic recurrence, remission, first line treatment in metastatic BC, further line of treatment in metastatic BC and death, over a lifetime horizon. Utility weights, using Portuguese tariffs, were based on EQ-5D-3L results from the KATHERINE study for iDFS, non-metastatic recurrence and remission. For metastatic disease, published data (Lloyd et al., 2006) was used. Portuguese-specific disease management resource use was based on a panel of clinical experts and on Portuguese diagnosis-related group microdata. National legislation and official drug cost databases were the main sources for unit costs. The analysis was conducted from the National Health Service perspective, assuming a 4% annual discount rate for costs and consequences. Deterministic and probabilistic sensitivity analyses were conducted to assess the robustness of the model and its results.

RESULTS: T-DM1 increased average life expectancy by 1.60 life years (LY) or 1.13 quality adjusted life years (QALY). Despite a decrease in average follow-up costs due to lower transition to metastatic health states, TDM-1 showed overall higher costs due to the cost of the drug. The estimated incremental cost-effectiveness ratios were 11,828€/LY and 16,715€/QALY. Deterministic sensitivity analyses showed that results are robust to most scenarios but sensitive to the time horizon, discount rate, and iDFS extrapolation options.

CONCLUSIONS: T-DM1 resulted in increased life expectancy and quality-adjusted life expectancy compared with trastuzumab. This cost-effectiveness model was considered valid to support a reimbursement decision in Portugal.