Fulvestrant 500 mg in postmenopausal patients with metastatic breast cancer: the initial clinical experience.

Background: Fulvestrant 500 mg is currently approved for the treatment of postmenopausal women with hormone receptor-positive metastatic breast cancer after failure of prior endocrine therapies.

Methods: A total of 117 postmenopausal women with metastatic breast cancer, who experienced progression after previous endocrine therapies, were treated with fulvestrant 500 mg between January 2012 and June 2014. Clinical response, time to progression (TTP) and adverse events were investigated.

Results: Ninety-nine patients had recurrent breast cancer and 18 patients had stage IV disease. Patients had received a median of two endocrine therapies and a median of two chemotherapies, prior to fulvestrant. There were 10 patients with partial response, 39 patients with long stable disease, 18 patients with stable disease, and 50 patients with progressive disease, so that the objective response rate was 8.5 %, with a clinical benefit rate of 41.9 %. The median TTP was 6.1 months. The absence of liver metastases, a small number of previous chemotherapies, and the longer duration of first-line endocrine therapy were positively correlated with TTP in univariate analysis. In multivariate analysis, a significant association was observed between TTP and duration of first-line endocrine therapy. Serious adverse events were observed in one patient with pulmonary embolism and in one patient with psychiatric symptoms.

Conclusions: Fulvestrant 500 mg is an effective and well-tolerated treatment for postmenopausal women with metastatic breast cancer that had progressed after prior endocrine therapies. Patients with acquired resistance to endocrine therapies might be good candidates for fulvestrant therapy regardless of the number of prior endocrine treatments.