PSA flare with abiraterone in patients with metastatic castration-resistant prostate cancer.

BACKGROUND: The aim of this study was to assess early serum prostate-specific antigen (PSA) changes in patients treated with abiraterone and to correlate those changes with clinical outcome.

PATIENTS AND METHODS: We retrospectively evaluated 103 patients with castrate-resistant prostate cancer (CRPC) treated with compassionate use of abiraterone in Romagna, Italy. In these patients, serum PSA levels were monitored every 4 weeks, and a time course of serum PSA levels was obtained. The PSA flare phenomenon was evaluated. The log-rank test was applied to compare survival between groups of patients according to early PSA level changes.

RESULTS: Of 103 patients, 43 (41.7%) had an immediate PSA response, whereas 9 (8.7%) had an initial PSA flare. Of the 9 patients with PSA flare, 5 attained a subsequent PSA response. The temporary PSA flare exceeded baseline values by a median of 19.7% (range, 5%-62.9%). The median PFS of the 9 patients in the PSA-flare group was higher compared with patients without the PSA flare (10.5 vs. 6.4 months; P = .0999) but was similar to the subgroup of patients with immediate PSA response (10.5 vs. 10.7 months; P = .7019). In the multivariate analysis, only the PSA response remained as a predictor of progression-free survival (PFS) (P < .0001) and overall survival (OS) (P = .0003), respectively.

CONCLUSION: PSA flare occurs not infrequently in patients with CRPC who respond to abiraterone. Patients should be informed of this possible PSA flare phenomenon.