Exploring Radiographic Progression-Free Survival in Diverse Subgroups of Metastatic Hormone-Sensitive Prostate Cancer: Comparative Efficacy of Abiraterone and Enzalutamide

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Abstract
Background/Objectives: Metastatic hormone-sensitive prostate cancer (mHSPC) is a biologically heterogeneous disease in which treatment intensification with androgen receptor pathway inhibitors has significantly improved clinical outcomes. However, direct comparative evidence between abiraterone and enzalutamide remains limited. We aimed to evaluate radiographic progression-free survival (rPFS) in patients with mHSPC treated with first-line abiraterone or enzalutamide and to perform exploratory subgroup analyses according to baseline clinical and laboratory characteristics. Methods: This retrospective single-center study included patients with mHSPC who received first-line abiraterone or enzalutamide in combination with androgen deprivation therapy. Baseline demographic, clinical, and laboratory characteristics were collected retrospectively. The primary endpoint was rPFS. Survival was analyzed using the Kaplan–Meier method and compared using the log-rank test. Results: A total of 172 patients were included, of whom 84 received abiraterone and 88 received enzalutamide. The median follow-up duration was 24.7 months (95% CI 21.5–27.9). In the overall population, median rPFS was comparable between the abiraterone and enzalutamide groups (50 vs. 49 months, p = 0.21). However, enzalutamide was associated with significantly longer rPFS among patients aged p = 0.02), those with baseline hemoglobin ≥12 g/dL (HR 0.36, 95% CI 0.15–0.85; p = 0.01), and those with baseline ALP < 147 U/L (HR 0.43, 95% CI 0.19–0.98; p = 0.04). No significant differences were observed in other subgroups. Conclusions: rPFS was comparable between abiraterone and enzalutamide in the overall mHSPC population. However, enzalutamide was associated with longer rPFS in patients aged <70 years and in those with preserved hemoglobin and lower ALP levels. These findings suggest that baseline clinical and laboratory characteristics may influence treatment outcomes and should be prospectively validated.

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