OBJECTIVES: Approximately 7,770 new patients are diagnosed annually with breast cancer in Greece and 25% of them have human epidermal growth factor receptor 2 (HER2+) disease. 49% of newly diagnosed HER2+ patients have early-stage breast cancer (eBC). Based on a physician survey (N=95), 44% of patients receive neo-adjuvant treatment, of whom 33.7% have residual disease and require additional treatment in the adjuvant setting. The objective of this study was to evaluate the cost-effectiveness of trastuzumab emtansine (T-DM1) for the adjuvant treatment of patients with residual invasive HER2+ eBC after neoadjuvant taxane-based and HER2-targeted therapy, from the third-party payer perspective (EOPYY) in Greece.

METHODS: A Markov model was developed to assess the quality-adjusted life years (QALYs) and costs associated with T-DM1 versus trastuzumab, over a lifetime horizon. Efficacy data and patient baseline characteristics were sourced from the KATHERINE trial. Costs were estimated from the third-party payer perspective (2022 values). A 3.5% discount rate was applied to both costs and health outcomes. Uncertainty was explored via probabilistic sensitivity analysis (PSA).

RESULTS: The lifetime costs associated with T-DM1 and trastuzumab were estimated at €89,539 and €86,757, respectively. T-DM1 was associated with 1.59 gained QALYs compared to trastuzumab (13.49 vs. 11.90) and 2.02 gained life years (17.49 vs. 15.46). The results indicated that T-DM1 was cost-effective compared to trastuzumab, with an incremental cost-effectiveness ratio (ICER) of €1,753 per QALY gained. PSA confirmed the robustness of the results, with 99.7% probability of T-DM1 being cost-effective at a willingness to pay (WTP) threshold 1-3 times the GDP per capita.

CONCLUSIONS: T-DM1 is likely to be a cost-effective treatment option for patients with residual invasive HER2+ eBC in Greece. The results indicated that the reduced likelihood of recurrence provided by treatment with T-DM1 would contribute in creating cost-offsets due to the avoidance of more costly metastatic treatments.