• Verin Lertjanyakun, Nathorn Chaiyakunapruk, Susumu Kunisawa, and Yuichi Imanaka.
• Department of Healthcare Economics and Quality Management, Graduate School of Medicine, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
• Pharmacoeconomics. 2018 Sep 1; 36 (9): 1113-1124.

BackgroundExemestane (EXE), exemestane + everolimus (EXE + EVE), toremifene (TOR), and fulvestrant (FUL) are second-line endocrine therapies for postmenopausal hormone receptor-positive (HR +)/human epidermal growth factor receptor 2-negative (HER2 -) metastatic breast cancer (mBC) in Japan. Although the efficacy of these therapies has been shown in recent studies, cost-effectiveness has not yet been determined in Japan.ObjectiveThis study aimed to examine the cost-effectiveness of second-line endocrine therapies for the treatment of postmenopausal women with HR + and HER2 - mBC.MethodsA Markov model was developed to analyze the cost-effectiveness of the therapies over a 15-year time horizon from a public healthcare payer's perspective. The efficacy and utility parameters were determined via a systematic search of the literature. Direct medical care costs were used. A discount rate of 2% was applied for costs and outcomes. Subgroup analysis was performed for non-visceral metastasis. A series of sensitivity analyses, including probabilistic sensitivity analysis (PSA) and threshold analysis were performed.ResultsBase-case analyses estimated incremental cost-effectiveness ratios (ICERs) of 3 million and 6 million Japanese yen (JPY)/quality-adjusted life year (QALY) gained for TOR and FUL 500 mg relative to EXE, respectively. FUL 250 mg and EXE + EVE were dominated. The overall survival (OS) highly influenced the ICER. With a willingness-to-pay (WTP) threshold of 5 million JPY/QALY, the probability of TOR being cost-effective was the highest. Subgroup analysis in non-visceral metastasis revealed 0.4 and 10% reduction in ICER from the base-case results of FUL5 500 mg versus EXE and TOR versus EXE, respectively, while threshold analysis indicated EVE and FUL prices should be reduced 73 and 30%, respectively.ConclusionAs a second-line therapy for postmenopausal women with HR +/HER2 - mBC, TOR may be cost-effective relative to other alternatives and seems to be the most favorable choice, based on a WTP threshold of 5 million JPY/QALY. FUL 250 mg is expected to be as costly and effective as EXE. The cost-effectiveness of EXE + EVE and FUL 500 mg could be improved by a large price reduction. However, the results are highly sensitive to the hazard ratio of OS. Policy makers should carefully interpret and utilize these findings.

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