Does androgen suppression enhance the efficacy of postoperative irradiation? A secondary analysis of RTOG 85-31

Objectives. To evaluate the effect of immediate androgen suppression in conjunction with standard external beam irradiation (RT) versus RT alone on a group of men after prostatectomy who had indications for adjuvant treatment. Methods. A national prospective randomized trial (Radiation Therapy Oncology Group [RTOG] 85-31) comparing standard external beam RT plus immediate androgen suppression versus external beam RT alone with delayed hormonal treatment at relapse was initiated for patients with locally advanced adenocarcinoma of the prostate. One hundred thirty-nine of the patients in this trial had indications for adjuvant treatment after prostatectomy (eg, capsular penetration, seminal vesicle involvement). Seventy-one of the patients received RT with immediate androgen suppression (luteinizing hormone-releasing hormone [LHRH] agonist); 68 patients received RT alone with hormonal manipulation instituted only at the time of relapse. Results. With a median follow-up of 5 years, the estimated progression-free survival rate (failure defined as prostate-specific antigen [PSA] greater than 0.5 ng/mL) was 65% for the men who received combination therapy and 42% for those treated by RT alone with hormones reserved for relapse (P = 0.002). Differences in the rates of freedom from biochemical relapse were observed when failure was defined as PSA of 1.0 to 5.9 ng/mL (71% versus 46%; P = 0.008) and PSA greater than 4.0 ng/mL (76% versus 55%; P = 0.05), respectively. No differences were observed between the groups with respect to the end points of local control, distant failure, and overall survival. The use of immediate androgen suppression (ie, LHRH agonists) and the absence of pathologic nodal involvement were independently associated with prolongation of freedom from biochemical relapse by multivariate analysis. Conclusions. Patients with prostate cancer and indications for postoperative RT should be considered for combined RT and hormonal manipulation. Because statistically significant advantages for this experimental approach could not be defined for all end points studied (in particular, overall survival), efforts should be made to enroll these patients in the recently activated RTOG trial (96-01) comparing RT plus placebo to the combination of RT plus Casodex in the postoperative setting. (C) 1999, Elsevier Science Inc.