Cost-utility analysis of trastuzumab deruxtecan versus trastuzumab emtansine as second-line treatment for HER2-positive metastatic breast cancer.

BACKGROUND: This study evaluated the cost-effectiveness of trastuzumab deruxtecan (T-DXd) versus trastuzumab emtansine (T-DM1) as second-line treatment for HER2-positive metastatic breast cancer from the perspective of the Chinese healthcare system. RESEARCH DESIGN AND METHODS: A partitioned survival model was developed based on the Asian subgroup of the DESTINY-Breast03 trial. The model adopted a 3-week cycle length and a lifetime horizon. Quality-adjusted life years (QALYs) were used as the primary outcome measure, and the incremental cost-effectiveness ratio (ICER) was calculated. Deterministic and probabilistic sensitivity analyses were performed to assess model robustness. RESULTS: At a willingness-to-pay (WTP) threshold of RMB 298,995/QALY (three times China's per capita GDP in 2025), T-DXd provided an additional gain of 1.45 QALYs at an incremental cost of 499805 RMB, resulting in an ICER of RMB 343989.08/QALY (95% PI: 320688.31- 352510.34). Deterministic sensitivity analysis identified PFS utility value and T-DXd-related costs as key drivers of the ICER. The probabilistic sensitivity analysis showed that at a WTP threshold of approximately RMB 340,000/QALY, the probability of T-DXd being cost-effective was 50%. CONCLUSION: T-DXd does not demonstrate a cost-effectiveness advantage over T-DM1 at the current WTP threshold in China. However, given the ICER's proximity of the threshold, price reductions or regional economic variation may improve its cost-effectiveness.