Complete androgen blockade as second-line hormone manipulation and delay of chemotherapy in metastatic prostate cancer

Abstract

e16141 Background: Complete androgen blockade (CAB) after failure of castration or androgen receptor blocker (ARB) has not shown to prolong survival in patients with metastatic prostate cancer, unlike docetaxel-based chemotherapy. The widely variable clinical benefit seen with CAB as second-line hormone manipulation still justifies the identification of the patients to whom it should be offered. Objective: to evaluate progression-free survival (PFS) and overall survival (OS) in patients treated with CAB after failure of castration or ARB and to identify clinical predictors of benefit. Methods: We performed a retrospective analysis of all patients with metastatic prostate cancer treated with CAB as second-line hormone manipulation in a single institution after September 2005. OS and PFS were estimated using Kaplan-Meyer plots. We identified 78 patients and evaluated correlations of prostate specific antigen (PSA), Gleason scores, age, type and length of first-line hormone manipulation with OS and PFS during CAB. Fifty-four patients had failed castration and 24 had failed ARB. Forty-four patients received chemotherapy after failing CAB. Results: With a median follow-up of 21 months, median PFS with CAB was 12 months (CI 6.8–17.2). We did not find any correlation of PFS with type of first-line hormone manipulation (castration vs ARB, p = 0.10), age group (≤70 or >70 years old, p = 0.10), level of PSA at diagnosis (≤50 or >50 ng/mL, p = 0.17) or length of first-line hormone manipulation (≤14m vs >14 m, p = 0.78). There was no significant correlation between PFS and Gleason score at diagnosis (score ≤7 or >7, p = 0.25), nor between the level of testosterone at the beginning of CAB and PFS. Median OS for patients on CAB after failing castration was 36 months (CI 24–48), and median OS of patients on chemotherapy was not reached at 9.5 months follow-up. Conclusions: Based on a PFS of 12 months, OS of 36 months and good patient tolerance, we believe CAB should still be used in CRPC, prior to initiation of chemotherapy. Predictors of clinical benefit are still to be identified. No significant financial relationships to disclose.