Enzalutamide Versus Abiraterone After Docetaxel in Metastatic Castration-Resistant Prostate Cancer: Real-World Outcomes and Exploratory Prognostic Stratification

Background/Objectives: Enzalutamide and abiraterone acetate are commonly used androgen receptor pathway inhibitors in metastatic castration-resistant prostate cancer (mCRPC), including after docetaxel. However, real-world outcomes remain heterogeneous, and simple prognostic markers may help describe this variability. This study aimed to describe survival outcomes with enzalutamide and abiraterone acetate after docetaxel and to explore the prognostic value of a routine clinical-inflammatory risk classification. Methods: This retrospective single-center study included 136 patients with mCRPC treated with enzalutamide or abiraterone acetate after docetaxel. A composite risk classification was defined using four routinely available variables: pan-immune-inflammation value (PIV) > 457.99, time to castration resistance < 12 months, baseline hemoglobin ≤ 12 g/dL, and Gleason score ≥ 8. One point was assigned for each adverse factor, and patients were classified as low, moderate, or high risk. Overall survival (OS) was assessed using Kaplan–Meier estimates and Cox regression. The prognostic score and Cox regression-based nomogram were evaluated as exploratory tools. Results: Of the 136 patients, 8 (5.9%) were classified as low risk, 67 (49.3%) as moderate risk, and 61 (44.9%) as high risk. Median OS was not reached in the low-risk group, compared with 33.84 months in the moderate-risk group and 9.66 months in the high-risk group. In multivariable analysis, high-risk status was independently associated with worse OS (HR = 9.87; 95% CI: 2.38–40.92; p = 0.002). No statistically significant OS difference was observed between enzalutamide and abiraterone acetate in this non-randomized cohort (HR = 1.36; 95% CI: 0.90–2.06; p = 0.142). Conclusions: In this real-world post-docetaxel mCRPC cohort, no statistically significant OS difference was observed between enzalutamide and abiraterone acetate; however, the study was not designed to establish comparative effectiveness or therapeutic equivalence. The exploratory risk classification based on routine clinical and inflammatory variables was associated with distinct survival outcomes. External validation is required before clinical application.