Bicalutamide during and after radiation therapy reduced the risk of progression and the risk of metastatic disease in men with a rising prostate-specific antigen (PSA) following radical prostatectomy for prostate cancer, researchers reported at the ASCO Genitourinary Cancers Symposium held February 17-19 in Orlando, Florida. The benefits of bicalutamide were evident across subgroups in the RTOG 9601 trial, and the addition of bicalutamide did not increase toxicity substantially.
The phase III randomized, placebo-controlled study was initiated in the mid-1990s, and after a median of 7 years of follow-up, the primary endpoint of overall survival has still not been met, with not enough events, said lead author William Shipley, MD, Massachusetts General Hospital, Boston. “This study provides proof of principle, and it can serve as a cornerstone for other studies.”
The study included 771 men with a median age of 65 years who had undergone radical prostatectomy and had disease outside the prostate or had positive margins but were lymph node-negative. Elevated PSA was ≤4 ng/ mL at study entry.
Patients were randomized either to radiation therapy of 64.8 Gy plus bicalutamide 150 mg daily or the same dose and schedule of radiation therapy plus placebo. At a median follow-up of 7 years, 95% of patients completed treatment as planned. Compliance with daily oral tablets was 84% in the bicalutamide-containing arm and 92% in the placebo arm. Freedom from progression was documented in 57% versus 40%, respectively, a highly significant difference favoring bicalutamide (P <.0001). Freedom from progression was superior with bicalutamide across all subgroups, Shipley said.