OBJECTIVES: Single-agent chemotherapy is the standard treatment for metastatic triple-negative breast cancer (mTNBC), but its efficacy is unsatisfactory. Although sacituzumab govitecan (SG) showed superiority over chemotherapy in improving overall survival, it is not approved in Japan and its cost-effectiveness is not necessarily clear. This study aimed to evaluate the cost-effectiveness of SG from the payer’s perspective in Japan.

METHODS: A partitioned survival analysis model was developed to predict costs and quality-adjusted life years (QALYs) in SG and chemotherapy groups. Survival data were derived from the phase III ASCENT study. Drug prices for SG were estimated based on foreign prices. Other cost parameters were estimated by using the JMDC calims database. Lifetime horizon and discount rate of 2% was applied. Utility weights were estimated based on previous studies. The incremental cost-effectiveness ratio (ICER) of SG compared with chemotherapy was estimated. Sensitivity analysis (SA) was performed to assess parameter uncertainty.

RESULTS: Compared with chemotherapy, SG incurred an additional cost of JPY 16,141,987 and conferred an additional 0.414 QALY. This resulted in the ICER of JPY38,961,498/QALY gained. SA showed that the parameter with the largest influence was utility of SG group in progression-free state, and the ICER ranged from JPY29,508,037 to JPY70,648,542/QALY.

CONCLUSIONS: Applying the willingness to pay threshold of JPY15 million/QALY and foreign drug price, SG was not cost-effective compared to chemotherapy. In the future, it would be necessary to incorporate a cost-effectiveness perspective in the pricing of cancer treatment in Japan.