Outcomes of first subsequent taxane (FST) therapy in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) who previously received docetaxel intensification (DI) for metastatic castration-sensitive prostate cancer (mCSPC).

Abstract

72 Background: The management of advanced prostate cancer continues to rapidly evolve, particularly with earlier use of survival prolonging therapies in mCSPC. Though approved prior to the use of intensification therapy in mCSPC, taxane-based chemotherapies remain a relevant option for pts with mCRPC. However, there is little evidence determining outcomes of taxane chemotherapies as FST in mCRPC pts who received DI in mCSPC. The purpose of this study is to compare outcomes between the survival prolonging taxanes, docetaxel (D) and cabazitaxel (C), as FST after DI. Methods: New patient consults seen at the Cross Cancer Institute from 1 July 2014 to 31 Dec 2020 were reviewed. Pts were considered eligible if they received DI for mCSPC and then received either D or C in mCRPC. Variables of interest were collected from the electronic medical record. The primary endpoint was ≥50% PSA response at 12 weeks relative to baseline for FST. Secondary endpoints included OS from mCSPC diagnosis, as well as PFS and OS from FST start date. PSA responses were compared using chi-squared test and time-based endpoints were compared using the Kaplan-Meier method. Results: 34 pts were identified: D = 22, C = 12 as FST. 91.2% of pts (D 95.5% vs C 83.3%) received FST in 2nd line mCRPC. Median age at diagnosis (63.1 vs 67.1 yrs, p = 0.236) and median time to CRPC (18.6 vs 14.2 mos, p = 0.079) were similar for D and C, respectively. Median time to FST (24.1 vs 34.6 mos, p = 0.036) and OS from mCSPC diagnosis (30.9 vs 52.7 mos, p = 0.002) were significantly shorter for pts receiving C vs D. PSA responses occurred in 40.9% of pts treated with D compared to 25.0% treated with C (p = 0.645). There was no significant difference in median PFS (2.7 vs 3.5 mos, p = 0.727) or median OS (11.4 vs 8.1 mos, p = 0.132) from time of FST for pts treated with D vs C, respectively. Conclusions: Both D and C demonstrated activity as FST after DI in mCSPC. Pts who received C had shorter time to FST and OS from mCSPC. The reasons for this may reflect clinician preference for C in pts with aggressive or rapidly progressing disease. No difference was found in PSA response, PFS, or OS from FST with D compared to C. While limited by its retrospective nature and small sample size, this study suggests that D is active as FST despite treatment with DI in mCSPC.