Prognostic value of PSA kelim score in high-volume mCSPC patients treated with abiraterone or enzalutamide: a single-center retrospective study

BACKGROUND: The use of androgen receptor pathway inhibitors (ARPIs), such as abiraterone and enzalutamide, in combination with androgen deprivation therapy (ADT), has significantly enhanced outcomes in metastatic castration-sensitive prostate cancer (mCSPC). However, validated early prognostic markers to guide treatment decisions are still limited. The PSA Kelim Score, a simplified kinetic model based on PSA kinetics, may provide a practical method for early risk assessment. METHODS: We conducted a retrospective study of 146 high-volume mCSPC patients treated with abiraterone or enzalutamide plus ADT. The PSA Kelim Score, calculated from three PSA measurements within the first 100 days of therapy (PSA₃/PSA₁), was used to classify patients into favorable (< 1) or unfavorable (≥ 1) PSA kinetics. The primary endpoint was progression-free survival (PFS). Kaplan-Meier and Cox regression analyses were employed to assess the relationships between the PSA Kelim Score, treatment type, and survival outcomes. RESULTS: Patients with favorable PSA kinetics (PSA Kelim Score < 1) experienced significantly longer median PFS compared to those with unfavorable PSA kinetics in both treatment groups (log-rank p < 0.001). Multivariate Cox analysis confirmed that unfavorable PSA kinetics (PSA Kelim Score ≥ 1) were independently associated with shorter PFS (HR = 2.10; 95% CI: 1.45-3.05; p < 0.001). No significant difference in PFS was observed between abiraterone and enzalutamide within each PSA Kelim subgroup. CONCLUSION: The PSA Kelim Score seems to be a promising and practical prognostic biomarker in high-volume mCSPC. Early PSA decline (Kelim < 1) correlates with better outcomes, regardless of ARPI type. Incorporating it into clinical decision-making may allow for timely treatment adjustments. Prospective validation is needed.