Clinical activity of fulvestrant in metastatic breast cancer previously treated with endocrine therapy and/or chemotherapy

Background/aims We conducted a retrospective analysis of the clinical activity of fulvestrant in postmenopausal women with hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) previously treated with endocrine therapy and/or chemotherapy. Methods We reviewed the medical records of all patients with MBC treated at Samsung Medical Center between January 2009 and August 2016. Patients received fulvestrant 250 mg intramuscularly every 28 days (from January 2009 to November 2010) or 500 mg intramuscularly every 28 days (from December 2010 to August 2016). Tumor responses were assessed every 8 weeks and at the end of treatment, as well as when disease progression was suspected. Results A total of 84 patients were included in this study. A median of two previous endocrine treatments had been performed; 79% of the patients had received two or more endocrine treatments. Forty-five patients (54%) had been treated with chemotherapy for MBC before the fulvestrant treatment course. Visceral metastasis was found in 49 patients (58%). The estimated median progression-free survival and overall survival were 4.4 months (95% confidence interval [CI], 3.4 to 5.5) and 32.5 months (95% CI, 17.6 to 47.4), respectively. The disease control rate was 40.5% (95% CI, 30.5 to 51.5); partial response was observed in 16% of the patients and stable disease was observed in 25% of the patients. The most frequently reported adverse reactions were mild-to-moderate grade myalgia (10.5% of the patients), injection site pain (7%), and fatigue (7%). Fulvestrant was generally well tolerated. Conclusion Fulvestrant showed encouraging clinical activity and favorable feasibility in postmenopausal women with MBC who had been treated with multiple endocrine therapies and/or cytotoxic chemotherapies.