Comparative Prognostic Impact of Two-Dimensional and Three-Dimensional Computed Tomography-Based Sarcopenia Indices in Metastatic Castration-Sensitive Prostate Cancer.

OBJECTIVES: This study evaluated and compared the prognostic significance of three different computed tomography (CT)-based radiological indices of sarcopenia-skeletal muscle index (SMI), psoas muscle index (PMI), and three-dimensional (3D) psoas muscle volume index (PVI)-in patients with metastatic castration-sensitive prostate cancer (mCSPC). METHODS: We retrospectively reviewed 120 patients diagnosed with mCSPC (2003-2022). Baseline muscle parameters were calculated from diagnostic CT scans. Sarcopenia was defined using the Martin criteria for SMI, and optimal cut-offs derived from maximally selected rank statistics for PMI (4.08 cm2/m2) and PVI (92 cm3/m2). Associations of these indices with age, overall survival (OS), and prostate cancer-specific survival (PCSS) were evaluated. RESULTS: Advancing age was significantly associated with SMI (OR: 1.05, p = 0.036) and PVI-defined sarcopenia (OR: 1.09, p < 0.001), with a non-significant trend for PMI (OR: 1.06, p = 0.069). Survival analysis revealed that sarcopenia by all three indices was significantly associated with worse OS (SMI [HR: 1.88, p = 0.032], PMI [HR: 2.19, p = 0.016], and PVI [HR: 2.07, p = 0.013]). In multivariable analyzes, SMI (HR: 1.86, p = 0.042), PMI (HR: 3.73, p < 0.001), and PVI (HR: 2.46, p = 0.006) remained independent risk factors for poorer OS. No significant impacts were observed for PCSS. CONCLUSIONS: When using body physique-adjusted or mathematically optimized thresholds, all three easily and rapidly measurable radiological indices (SMI, PMI, and PVI) may serve as potential, independent prognostic indicators for OS in patients with mCSPC.