BACKGROUND: Breast cancer is the most common cancer among female.The CHINA COFIRM study supported that the superior clinical beneft of fulvestrant 500 mg in women with ER-positive metastatic breast cancer in China experiencing progression following prior endocrine therapy.It is important to ensure that fulvestrant 500 mg are effective and economical. OBJECTIVES: We conducted a study to assess the cost-effectiveness of fulvestrant 250 mg versus 500 mg in postmenopausal women with ER-positive metastatic breast cancer in China. METHODS: A Markov model was developed to evaluate costs and health outcomes represented as quality adjusted life months(QALMs) gained.Input data were obtained from CHINA COFIRM study and the other public literatures. The results were expressed as incremental cost per QALM gained. A base-case analysis was established based on a hypothetical cohort of 1000 patients. A one-way deterministic sensitivity analysis explored the impact of uncertainty in the model parameters on results, and probabilistic uncertainty was assessed through a Monte Carlo probabilistic sensitivity analysis. RESULTS: The incremental total cost of fulvestrant 500 mg was $1582.995 and incremental QALM was 0.355, thus the ICER was $4462.406 per QALM gained.Compared with threshold of WTP $2209.041/QALMs in China, the fulvestrant 500 mg is dominated strategy in postmenopausal women with ER-positive metastatic breast cancer in China.The price of the fulvestrant 500 mg have the greatest influence on the results of the study model. CONCLUSIONS: From the perspective of the Chinese healthcare system, fulvestrant 500mg is not a costeffective strategy compared with fulvestrant 250mg for ER-positive advanced breast cancer.