Prostate-specific antigen flare induced by cabazitaxel-based chemotherapy in patients with metastatic castration-resistant prostate cancer

Background A prostate-specific antigen (PSA) flare occurs in about 15% of metastatic castration-resistant prostate cancer (mCRPC) patients receiving docetaxel. This flare has no standard definition. Its impact on treatment efficacy is unclear. We sought to evaluate the incidence and characteristics of PSA flare on cabazitaxel, and its impact on survival. Methods Multicentre retrospective review of consecutive patients treated with cabazitaxel second-line chemotherapy for mCRPC. Collection of baseline characteristics, disease history and PSA levels before and during cabazitaxel therapy. Overall survival (OS) and radiological/clinical progression-free survival (PFS) for patient groups corresponding to different definitions of PSA flare estimated by the Kaplan-Meier method and compared using the log-rank test. Results Overall, 125 patients were included. Median PFS and OS were 6.5 and 13.3 months, respectively. Depending upon the definition used, flare incidence ranged from 8.3% to 30.6%. The flare lasted <2.6 months. A PSA flare followed by a ≥50% decrease was associated with a median PFS and OS of 11.2 and 25.2 months, respectively. Median PFS and OS for a ≥30% rather than ≥50% decrease were 10.4 and 16.5 months. These outcomes were not significantly different from those in patients with immediate PSA decreases of ≥50% or ≥30% from baseline, but were significantly better than in patients experiencing no PSA decrease (p = 0.006 and 0.015, respectively, for OS). Conclusion The PSA response to cabazitaxel, with or without initial flare, was associated with a strong survival benefit. The taxane-induced flare during the first 12 weeks of therapy can be ignored when evaluating PSA response.