Efficacy of Ga-68-PSMA PET/CT-derived whole-body volumetric parameters in predicting response to second-generation androgen receptor axis-targeted therapy, and the prognosis in metastatic hormone-refractory prostate cancer patients

Abstract

Introduction The present study investigates the role of Ga-68-PSMA PET/CT-derived whole-body metabolic and volumetric parameters in the prediction of treatment response and prognosis among metastatic hormone-refractory prostate cancer patients undergoing second-generation androgen receptor axis-targeted therapy (abiraterone or enzalutamide). Materials and methods This retrospective study included 44 metastatic hormone-refractory prostate cancer patients undergoing Ga-68-PSMA PET/CT, including 29 enzalutamide-treated and 15 abiraterone-treated patients. Results Of the 44 patients included in the study, 29 received enzalutamide and 15 received abiraterone. During treatment, the changes in PET parameters were correlated with the PSA (biochemical) response. More specifically, a positive correlation was noted between PSA response and percent change in TLP (Delta TLP) response, and there was concordance between the results (r = 0.652, k = 0.42, P < 0.001). Baseline PSA (P =0.05), high MTVw (P = 0.005), the increase in Delta PSA (P = 0.036), Delta TLP (P = 0.039) and percent change in MTV (Delta MTV) (P = 0.049) values were identified as factors associated with mortality risk.Multivariate analysis showed that PSA1 [odds ratio (OR): 1.005, 95% confidence interval (CI) 1.002-1.008, P = 0.004], Delta PSA (OR: 14.7, 95% CI 1.50-143.7, P = 0.02) and MTVw1 (OR: 11.4, 95% CI 1.11-116, 6, P = 0.04) were independent prognostic factors associated with mortality risk. Conclusion A statistically significant concordance and correlation was noted between Ga-68-PSMA PET/CT-derived whole-body metabolic parameters (Delta TLP and Delta MTV) and Delta PSA. In addition, the baseline PSA, Delta PSA, Delta TLP, Delta MTV and TMTV were identified as predictive factors for mortality risk.