Orlando, FL--The addition of the nonsteroidal antiandrogen bicalutamide (Casodex) to a luteinizing hormone-releasing hormone agonist (LHRHa) confers significant benefits over LHRH monotherapy as first-line treatment for advanced prostate cancer, according to a study presented by Japanese researchers at the American Society of Clinical Oncology annual meeting here.
For men with previously untreated advanced prostate cancer, these findings may indicate a role for maximal androgen blockade (MAB) as first-line treatment in this setting.
"Although MAB has been thought to be effective theoretically, it has not been proven clinically in the setting of castration plus flutamide until now. Our study shows the clear effect of MAB," said lead study author Hideyuki Akaza, MD, professor and chairman, department of urology, Institute of Clinical Medicine, University of Tsukuba.
These significant improvements were greater than those reported in a previous analysis of this study performed at a median of 15 months.
Benefit in grade C disease
Dr. Akaza said that an interesting observation of the study was the particular benefit of bicalutamide combination therapy in patients with grade C disease who showed the greatest improvement in TTP. Patients treated with LHRHa alone had a median TTP of 134 weeks, while median TTP has not yet been reached in patients receiving combination therapy (p<.001).
"We think that patients with stage C disease are good candidates for MAB therapy, especially for immediate MAB therapy, which is usually done in Japan," said Dr. Akaza.
He emphasized, however, that overall survival data are still pending, with interim data showing no difference between combination therapy and monotherapy (87.3% vs. 82.2%), but if a survival difference in favor of the combination group is demonstrated at further follow-up.
"MAB will be recommended in daily clinics," said Dr. Akaza.
The interim analysis also found that 77.5% of patients who had disease progression on LHRHa monotherapy responded to second-line bicalutamide, with a median time to response and duration of response of 4.14 and 39.57 weeks, respectively.
Of the patients who withdrew from bicalutamide after disease progression, 38.9% continued to show further response. The patients had median time to response and duration of response of 6.86 and 58.14 weeks, respectively.
Lower withdrawal rate
Overall, treatment-related withdrawal was lower in the bicalutamide combination therapy group than in the monotherapy group (8.8% vs. 10.9%, respectively). The low dropout rate is an important finding of this study, said Dr. Akaza.