Southwest Oncology Group S9921: Prolonged event-free survival in high-risk prostate cancer (PC) patients receiving adjuvant androgen deprivation

Abstract

5009 Background: Patients with adverse pathologic risk factors after radical prostatectomy are at high risk for biochemical relapse and eventual death from disease. Adjuvant hormonal therapy with or without chemotherapy may prolong event free survival. Methods: SWOG 9921 randomized 859 eligible high risk PC patients to receive 2 years of adjuvant combined androgen blockade (CAB) (goserelin + bicalutamide) with (433) or without (426) chemotherapy (mitoxantrone + prednisone). The primary endpoint is survival. The DSMC has approved this analysis. PSA was to be assessed every 3 mo for 5 yrs and then every 6 mo for 10 more yrs. PSA relapse was defined as 3 consecutive measurements > 0.2 ng/ml. Death w/o relapse is censored. The CAB only eligible group is being reported (n=426). Risk groups based on eligibility criteria are as follows: Risk Group 1= positive margins or extraprostatic extension only with Gleason 7; elevated PSA (pre-op > 15 ng/ml), or had a pre-op PSA > 10 ng/ml and a biopsy Gleason 7(N=113); Risk Group 2 = seminal vesicle invasion or Gleason >/= 8, but no positive nodes (N=240), Risk Group 3 =positive nodes (N=69), 397 patients from both arms who completed 2 years of CAB were assessed for time to testosterone (T) recovery. T was assessed every 6 mo until it reached the institutional lower limit of normal. The median follow-up time from randomization is 3.8 years. Results: See Table . The estimated median time to T recovery (> 50ng/ml) is 11.7 mo from the end of CAB (95% CI 11.3, 11.9 months). The 6 and 18 mo recovery rates were 16% and 89%. Of 17 deaths (including ineligibles), 7 were from prostate cancer; 4 from other cancers, one cardiovascular disease, and 5 from miscellaneous causes. Conclusions: These data indicate a markedly low PSA relapse and death rates in high risk PC patients who received CAB. This likely is the result of stage migration, patient selection and/or the effects of CAB itself. [Table: see text] [Table: see text]