Abstract P6-13-01: Cost-effectiveness of ado-trastuzumab emtansine (T-DM1) versus trastuzumab (H) for the adjuvant treatment of patients with residual invasive HER2+ early breast cancer in the US
Authors: Goertz Hans-Peter , Herrera-Restrepo Oscar , Wehler Elizabeth , Bilir Pinar , Antao Vincent , Jhuti Gurleen Singh 
Published: March 2020

Abstract
Objectives: Ado-trastuzumab emtansine (T-DM1) is a HER2-targeted antibody drug conjugate (ADC) indicated for the adjuvant treatment of patients with HER2+ early breast cancer (eBC) who have residual invasive disease after neoadjuvant taxane and trastuzumab-based treatment. In a phase 3 clinical trial (KATHERINE, NCT01772472), T-DM1 demonstrated a statistically significant 50% reduction in the risk of invasive BC recurrence or death compared with trastuzumab (H) (HR= 0.5, 95% CI 0.39-0.64; p&lt;0.001). This study explored the cost-effectiveness of T-DM1 use versus H from a US third-party payer perspective.
Methods: A Markov-based cost-effectiveness model with a lifetime horizon was developed to compare the clinical and cost outcomes of T-DM1 versus H from the US payer perspective. The model considered the population from the KATHERINE trial and included six health states: invasive disease-free, non-metastatic (locoregional) recurrence, remission, first- and second-line metastatic breast cancer (mBC), and death. Invasive disease-free survival (iDFS) projections over patients' lifetimes were derived from statistical extrapolation of the KATHERINE clinical trial data, while overall survival, estimated as the risk of death in each health state, was derived from several BC clinical trials and US life tables. The model included costs for treatments in all health states, except for remission and death. Dosing and treatment duration was from product prescribing information and/or published literature. Drug costs were estimated using the wholesale acquisition cost (WAC) for drugs from Medispan PriceRx. Additional costs included health state-related medical resource use, adverse events during iDFS, and costs associated with end of life. These costs were derived from Medicare physician and laboratory fee schedules, prescribing information for adverse event rates and the published literature for both adverse event and end of life costs. Health state utilities were derived from the KATHERINE clinical trial and the published literature. All costs were adjusted to 2019 US dollars.
Results: In the base case, T-DM1 dominated H (incremental costs: -$41,003, incremental quality-adjusted life years [QALYs]: 1.79, incremental life years [LYs]: 2.22). Results were driven by cost offsets observed in health states beyond iDFS. T-DM1 produced cost savings due to fewer patients with invasive recurrence, and hence, fewer patients undergoing first- and second-line mBC (e.g., $1,540 vs $6,684, $49,512 vs $85,795, and $35,204 vs $62,435 lifetime costs for T-DM1 and H in non-metastatic recurrence, first- and second-line mBC, respectively). The probabilistic sensitivity analysis found consistent cost savings in all iterations (T-DM1 was dominant 96.6% of the simulations). Scenario analyses showed that base case results remain robust across input variations.
Conclusions: The cost-effectiveness analysis shows that T-DM1 as an adjuvant therapy for patients with HER2-positive eBC who have residual invasive disease after neoadjuvant therapy is a dominant treatment option (less costly, more effective) compared to H in the US.
Citation Format: Hans-Peter Goertz, Oscar Herrera-Restrepo, Elizabeth Wehler, Pinar Bilir, Vincent Antao, Gurleen Singh Jhuti. Cost-effectiveness of ado-trastuzumab emtansine (T-DM1) versus trastuzumab (H) for the adjuvant treatment of patients with residual invasive HER2+ early breast cancer in the US [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-13-01.