Quantification of Metastatic Prostate Cancer Whole-Body Tumor Burden with 18F-FDG PET Parameters and Associations with Overall Survival After First-Line Abiraterone or Enzalutamide: A Single-Center Retrospective Cohort Study

Abstract

New biomarkers for metastatic prostate cancer are needed. The aim of this study was to evaluate the prognostic value of 18F-FDG PET whole-body tumor burden parameters in patients with metastatic prostate cancer who received first-line abiraterone or enzalutamide therapy. Methods: This was a retrospective study of patients with metastatic castration-sensitive prostate cancer (mCSPC, n 5 25) and metastatic castration-resistant prostate cancer (mCRPC, n 5 71) who underwent 18F-FDG PET/CT within 90 d 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 mo (interquartile range, 37.7-66.8 mo); the median OSs for patients with mCRPC and mCSPC were 27.8 and 76.1 mo, respectively (P, 0.001). On univariate analysis, the OS probability of mCRPC patients was significantly associated with plasma levels of alkaline phosphatase (hazard ratio [HR], 1.90; P, 0.001), plasma levels of lactate dehydrogenase (HR, 1.01; P, 0.001), hemoglobin levels (HR, 0.80; P 5 0.013), whole-body SUVmax (HR, 1.14; P, 0.001), the number of 18F-FDG-avid metastases (HR, 1.08; P, 0.001), whole-body metabolic tumor volume (HR, 1.86; P, 0.001), and TLG (HR, 1.84; P, 0.001). On multivariable analysis with stepwise variable selection, hemoglobin levels (HR, 0.81; P 5 0.013) and whole-body TLG (HR, 1.88; P, 0.001) 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, 18F-FDG PET WB TLG is independently associated with OS and might be used as a quantitative prognostic imaging biomarker.