QUANTIFICATION OF METASTATIC PROSTATE CANCER WHOLE-BODY TUMOR BURDEN WITH FDG PET PARAMETERS AND ASSOCIATIONS WITH OVERALL SURVIVAL AFTER FIRST LINE ABIRATERONE OR ENZALUTAMIDE: A SINGLE- CENTER RETROSPECTIVE COHORT STUDY

Abstract

RATIONALE: New biomarkers for metastatic prostate cancer are needed. The aim of this study was to evaluate the prognostic value of FDG-PET whole body tumor burden parameters in patients with metastatic prostate cancer who received first line abiraterone or enzalutamide therapy. METHODS: Retrospective study of patients with metastatic castration-sensitive (mCSPC, n = 25) and metastatic castration-resistant prostate cancer (mCRPC, n = 71) who underwent ¹⁸F-FDG-PET/CT within 90 days before first-line treatment with abiraterone or enzalutamide at a tertiary care academic cancer center. Whole-body tumor burden on PET/CT was quantified as metabolic tumor volume (MTV) and total lesion glycolysis (TLG) and correlated with overall survival (OS) probabilities using Kaplan-Meier curves and Cox models. RESULTS: The median follow-up in survivors was 56.3 months (IQR: 37.7, 66.8); the median OS for patients with mCRPC and mCSPC was 27.8 and 76.1 months (p<.001). On univariate analysis, the OS probability of mCRPC patients was significantly associated with plasma levels of alkaline phosphatase (HR: 1.90, p<.001) and lactate dehydrogenase (HR: 1.01, p<.001), hemoglobin levels (HR: 0.80, P = .013), whole body SUV_max (HR: 1.14, p<0.001), the number of FDG-avid metastases (HR: 1.08, p<0.001), whole body MTV (HR: 1.86, p<.001) and TLG (HR: 1.84, p<.001). In multivariable analysis with stepwise variable selection, hemoglobin levels (HR: 0.81, P = 0.013) and whole-body TLG (HR: 1.88, p<.001) were independently associated with OS. In mCSPC patients, no significant association was observed between these variables and OS. CONCLUSION: In patients with mCRPC receiving first-line treatment with abiraterone or enzalutamide, FDG PET WB TLG is independently associated with OS and might be used as quantitative prognostic imaging biomarker.