Phase II study of fulvestrant (Faslodex®) in castration resistant prostate cancer

BACKGROUND. Preclinical evidence supports the role of estrogen receptor signaling in prostate cancer. In this trial we investigated the tolerability and efficacy of fulvestrant, a pure estrogen receptor antagonist, in the treatment of castration resistant prostate cancer (CRPC). METHODS. Patients with CRPC were enrolled after written informed consent. Fulvestrant was administered by intramuscular injection at a dose of 500 mg on day 0, then 250 mg on day 14, day 28 and monthly thereafter. History, physical examination, serum prostate specific antigen (PSA) levels and toxicity was evaluated monthly. Radiographic studies were repeated every 3 months to assess disease. Treatment was continued until disease progression, unacceptable toxicity, non-compliance or consent withdrawal. RESULTS. Twenty patients were enrolled over a period of six months. All patients were Caucasians with median age of 69.5 years [range: 47-85 years]. Sixteen patients (80%) had radiological evidence of metastasis and four patients (20%) had rising PSA as the only evidence of progressive disease. Patients received a median of three treatment cycles of fulvestrant [range: 1-11]. Median time to progression was 4.3 months (95% confidence interval of 3-5.7 months) and median overall survival was 19.4 months (range: 9.9-19.4 months) after a median follow-up of 16 months. No patient showed ≥50% reduction in PSA or radiologic improvement. Few adverse events were noted, none of which were attributed directly to fulvestrant. CONCLUSION. Fulvestrant was well tolerated but failed to produce clinical or PSA response in men with CRPC.