Benefits of early and prolonged fulvestrant treatment in 848 postmenopausal advanced breast cancer patients.

Response to fulvestrant and survival in postmenopausal hormone-sensitive advanced breast cancer was investigated within a non-randomized, In-Practice Evaluation Program, with the aim of optimizing treatment decisions. 848 patients (median age 64 years; 52% co-morbidity; 78% prior palliative therapy; median 4 prior regimens) received monthly fulvestrant injections (250 mg/month) and were followed-up three-monthly for 9 months. Clinical benefit (PFS ≥ 24 weeks) occurred in 532/848 (62.7%); stable disease (SD) in 627/848 patients (74%), including 62 complete and 177 partial responses. Best response was delayed in 115 patients. Estimated 9-month overall survival (OS) was 89%; 9-month event-free survival (EFS) was 71%. Indicators of disease aggressiveness affected response and survival, but number of fulvestrant cycles was the key OS and EFS determinant. The patients with SD at 3 months benefitted from continued fulvestrant. Excluding deaths, 7 serious adverse events occurred (none attributable to fulvestrant). No new or unexpected safety issues arose; 90% of the patients and physicians rated fulvestrant tolerability as "very good" or "good". In the largest prospective, fulvestrant-treated cohort to date, advanced breast cancer patients achieving SD or better after 3 months of treatment gained survival benefit by prolonging fulvestrant therapy-independent of disease and treatment history.