Purpose: To provide a snapshot of toxicities and oncologic outcomes of Abiraterone (AA) and Enzalutamide (EZ) in a chemo-naïve metastatic castration-resistant prostate cancer (mCPRC) population from a longitudinal real-life multicenter cohort.
Methods: We prospectively collected data on chemo-naïve mCRPC patients treated with AA or EZ. Primary outcomes were PSA response, oncologic outcomes and toxicity profile. The Kaplan-Meier method was used to compare differences in terms of progression-free survival (PFS) between AA vs EZ and high- vs low-volume disease cohorts. Univariable and multivariable Cox regression analyses were performed to identify predictors of PFS. Toxicity, PSA response rates and oncologic outcomes on second line were compared with those observed on first line.
Results: Out of 137 patients, 88 received AA, and 49 EZ. On first line, patients receiving EZ had significantly higher PSA response compared with AA (95.9% vs 67%, p < 0.001), comparable toxicity rate (10.2% vs 16.3%, p = 0.437) and PFS probabilities (p = 0.145). Baseline PSA and high-volume disease were predictors of lower PFS probabilities at univariable analysis (p = 0.027 and p = 0.007, respectively). Overall, 28 patients shifted to a second-line therapy (EZ or radiometabolic therapy). Toxicity and PSA response rates on second line were comparable to those observed on first line (11.1% vs 12.4%, p = 0.77; 73.1% vs 77.4%, p = 0.62, respectively); 2-year PFS, cancer-specific and overall survival probabilities were comparable to those displayed in first-line cohort (12.1% vs 16.2%, p = 0.07; 85.7% vs 86.4%, p = 0.98; 71% vs 80.3%, p = 0.66, respectively).
Conclusions: Toxicity profile, PSA response rate and oncological outcomes were comparable between first-line and second-line courses in patients treated with either AA or EZ for mCRPC. Our findings showed the tolerability and oncological effectiveness, when feasible, of two lines of therapy other than chemotherapy.
Keywords: Androgen receptor targeted agent; Castration-resistant prostate cancer; High volume disease; Metastatic disease; Systemic therapy.