Initial report of RTOG 9601, a phase III trial in prostate cancer: Effect of anti-androgen therapy (AAT) with bicalutamide during and after radiation therapy (RT) on freedom from progression and incidence of metastatic disease in patients following radical prostatectomy (RP) with pT2-3,N0 disease and elevated PSA levels.

1 Background: To test if long term AAT when combined with RT in these patients (pts) with prostate cancer (PC) will improve cancer control outcomes as well as overall survival (OS). Methods: Post-RP pts with pT3,N0 or with pT2,N0 (and positive margins) who have an elevated PSA were entered on a phase III, double-blinded, placebo-controlled trial of RT alone (64.8 Gy in 1.8 Gy fractions) vs RT + AAT (24 months of bicalutamide, 150mg daily) during and after RT. The primary end point is OS. Results: From 3/98 to 3/03, 771 eligible pts (median age 65) were randomized to RT + AAT (387) or RT alone (383). Pretreatment characteristics were balanced. 672 (87%) had a PSA nadir after RP of < 0.5 ng/mL. 655 (85%) had an entry PSA value of <1.6, 115 (15%) had an entry PSA of 1.6-3.9. Median follow-up was 7.1 years. Actuarial OS at 7 years was 91% for RT + AAT and 86% for RT alone. Too few primary end-point events have occurred to allow a statistical comparison between groups. Freedom from PSA progression (FFP) at 7 years was 57% for RT + AAT and 40% for RT alone (P < 0.0001); for 226 pts with GS < 7 were 63% and 50% (P<0.02), for 411 GS 7 these were 55% and 39% (P<0.0006), and for 134 GS 8-10 were 56% and 26% (P < 0.0008). The 7-yr cumulative incidence of metastatic PC was less in the RT and AAT arm, 7% vs 13% in the RT arm (p<0.041). Late grade 3-4 toxicities were similar in both arms. By category the combined grade 3-4 toxicities for RT + AAT and RT alone were: bladder 6% vs 5% bowel 2% vs 1%, cardiac 3% vs 2%. Gynecomastia (mostly grades 1-2) differed significantly, 89% vs15%. In the RT + AAT arm grade 3 was the highest liver toxicity, which occurred in 3 pts. Conclusions: The addition of 24 months of bicalutamide 150 mg daily during and after RT significantly improved FFP and reduced the incidence of metastatic PC without adding significantly to RT toxicity. The significance of benefit in OS, as well analysis of risk-stratified subsets, wait longer follow-up. No significant financial relationships to disclose.