Retrospective registry evaluating the PSA flare phenomenon with cabazitaxel in metastatic castration-resistant prostate cancer (mCRPC).

Abstract

122 Background: PSA initial flare followed by a decrease is documented in up to 18% of mCRPC patients (pts) treated with docetaxel (D). There is no standard definition of this phenomenon, and its significance in terms of treatment efficacy and prognosis remains unclear. We evaluated the PSA flare incidence and characteristics with cabazitaxel (C), a new taxane developed to overcome D resistance, and its impact on outcome. Methods: A retrospective review of 84 consecutive pts (median 67 yrs) treated with C for mCRPC progressing during or after D was conducted in 8 French centers. Baseline characteristics, disease history, PSA values before and during C, overall survival (OS) and radiological or clinical progression-free survival (PFS) were collected. Results: At C initiation, most pts (84%) were ECOG 0-1, 59.5% had pain and 23.8% received ≥2 chemotherapy lines. Metastases were located in bone (92.9%), lymph nodes (48.8%) and visceral/soft tissues (9.5%). Median number of C cycles was 6 (range 2-14). Median OS and PFS from first C cycle were 16.4 and 6.7 months, respectively. Flare incidence, PFS and OS varied with the definition used (table). Definition [3] seems to us the most clinically relevant, and showed a close estimate of PFS compared to pts with immediate PSA decrease from baseline. We recommend to use this definition in clinical practice. Conclusions: PSA flare occurred in 16% pts treated with C and was associated with as good outcome as immediate responders. C should not be withdrawn prematurely in case of isolated initial PSA rise. This finding supports the PCWG 2 recommendation that early rise (prior to 12 weeks) with cytotoxics should be ignored in determining PSA response. [Table: see text]