Effect of neoadjuvant abiraterone acetate (AA) plus leuprolide acetate (LHRHa) on PSA, pathological complete response (pCR), and near pCR in localized high-risk prostate cancer (LHRPC): Results of a randomized phase II study.

Abstract

4521 Background: LHRPC is infrequently cured with prostatectomy (RP). To date neoadjuvant androgen deprivation therapy (ADT) has not improved outcomes and residual intra-prostatic androgens remain. AA lowers serum testosterone (T) and DHT to < 1 ng/dL and has improved survival in advanced PC. Methods: We conducted a neoadjuvant, phase II trial of AA/LHRHa in LHRPC. The primary aim was to evaluate intra-prostatic T/DHT with LHRHa vs LHRHa/AA. We report secondary endpoints of PSA, pCR and near pCR ([≤ 5mm residual tumor]) and safety. Eligibility: ≥ 3 positive biopsies and either Gleason ≥ 7 (4+3), T3, PSA ≥ 20 ng/mL or PSA velocity > 2 ng/mL/year. For the first 12 wks men were randomized to LHRHa or LHRHa/AA/prednisone (P) 5mg qd. After 12 wks, a prostate biopsy was done to measure T/DHT. Men received 12 more wks of LHRHa/AA/P followed by RP. Results: 58 men enrolled: 28 to initial LHRHa and 30 to initial AA/LHRHa. 2 withdrew prior to RP (1/group). Median age was 58 (50-75). pCR/near pCR was 14/56 (25%). Grade 3 AEs included elevated AST/ALT 5/58 (9%) and hypokalemia 3/58 (5%). No grade 4 mineralocorticoid-related AEs were observed. Conclusions: Neoadjuvant ADT with AA was well tolerated in LHRPC. PSA (<0.2) declines were high and achieved earlier on AA/LHRHa compared to LHRHa. The pCR/near pCR rates were higher for 24 wks AA (34%) than 12 wks AA (15%). No new safety signals were seen with AA used with P 5 mg. These results support further evaluation of aggressive ADT as neoadjuvant/adjuvant therapy for LHRPC. [Table: see text]