Objectives. To study the ability of nilutamide to induce prostate-specific antigen (PSA) responses in patients with hormone-resistant prostate cancer who had been exposed to prior antiandrogen therapy, because resistance to antiandrogens may be mediated by altered binding to a mutated or overexpressed androgen receptor and because an alternative antiandrogen may overcome such resistance. Nilutamide is a little used antiandrogen that has a chemical structure distinct from that of the other two antiandrogens, flutamide and bicalutamide.

Methods. Fourteen patients with hormone-resistant prostate cancer were treated with nilutamide 150 mg/day (n = 12) or 300 mg/day (n = 2). Seven had been treated with one prior antiandrogen (all with bicalutamide), five with both bicalutamide and flutamide, and two had received bicalutamide and prior chemotherapy.

Results. In a retrospective analysis, 7 (50%) of the 14 patients had a greater than 50% decline in their PSA level, and 4 of the 6 patients with bone pain experienced subjective improvement. The median duration of the PSA response was 11 months (range 2 to 28+) with 2 of the 7 patients still experiencing a PSA response. In addition, 3 patients (20%) had brief and minor PSA responses (less than 50%).

Conclusions. A subset of patients, whose disease progresses with prior antiandrogen therapy, may experience a PSA response to nilutamide. The role of nilutamide in such hormone-resistant patients deserves additional prospective study.