How Reliable Is the High-Volume Definition in Prostate Cancer Patients: The Potential Game-Changing Role of PSMA

Abstract Purpose To evaluate whether metabolic and volumetric data from Ga-68 PSMA PET CT performed during staging of denovo high-volume mCSPC patients who received docetaxel could be used to predict survival. Methods Forty-two denovo high-volume metastatic castration-sensitive prostate cancer patients, who received ADT + Docetaxel and underwent Ga-68 PSMA PET CT for staging, were included in the study. The association between patients' pathological data, all PSA measurements, treatments they received, and the data obtained from Ga-68 PSMA PET CT and progression-free and overall survival were examined. In the univariant analysis performed with the log-rank test, it was evaluated whether the difference between subgroups of variables was statistically significant in terms of survival. Variables found statistically significant were included in the multivariate analysis with the Cox hazard ratio model. Results In the multivariate analysis, PSMA-TV (primary) and PSMA-TV (WB) variables were shown to be independent negative predictors of overall survival. For the threshold value of 19.91 cc obtained for PSMA-TV (primary), HR was calculated as 6.31, 95% CI: 1.01-39.18, p: 0.048. For the threshold value of 1226.5 cc obtained for PSMA-TV(WB) variable, HR was calculated as 58.62, 95% CI: 2.55-1344.43, p:0.011. In our study, SUVmax (WB) variable was found to be an independent and negative predictor of progression-free survival. For the determined threshold value of 17.74, HR was calculated as 16.24, 95% CI: 1.18-22.76, p: 0.037. Conclusion Metabolic and volumetric data obtained from Ga-68 PSMA PET CT can be used to predict survival in denovo high-volume mCSPC. Our results show that ADT + Docetaxel receiving patients with high PSMA-TV (WB) values have a significantly worse prognosis. This situation reveals that the high-volume disease definition in the literature is insufficient for this group and that Ga-68 PSMA PET CT can play an important role in demonstrating the heterogeneity within the group.