BACKGROUND: Endocrine therapy is the preferred treatment for hormone-receptor (HR) positive metastatic breast cancer. In premenopausal patients, ovarian function suppression with goserelin in combination with anastrozole yielded promising results in phase II studies. Fulvestrant, a pure antioestrogen, yields high rates of disease stabilisation in postmenopausal women. Therefore, we investigated the feasibility and safety of fulvestrant plus goserelin in premenopausal women with HR-positive metastatic breast cancer.

METHODS: Premenopausal patients with metastatic breast cancer eligible for endocrine treatment received fulvestrant 250 mg and goserelin 3.6 mg every four weeks as first- to fourth-line therapy. Clinical benefit rate (CBR; response rate plus disease stabilisation ≥ 6 months) was defined as the primary study end-point. Time to progression (TTP) and overall survival (OS) were estimated using the Kaplan-Meier product limit method.

FINDINGS: Twenty-six patients received treatment as scheduled. 81% were pre-treated with tamoxifen and 69% had received prior aromatase inhibitors in combination with goserelin. The majority of patients (69%) presented with visceral metastases. Complete response was observed in a single patient, partial response in three and disease stabilisation ≥ 6 months in eleven patients, resulting in a CBR of 58%. Median TTP was 6 months (95%confidence interval (CI), 2.4-9.6) and OS 32 months (95%CI, 14.28-49.72), respectively.

INTERPRETATION: Results suggest that the combination of fulvestrant and goserelin offers promising activity in premenopausal patients and further investigation is warranted.