The role of [68Ga]Ga-PSMA-11 PET/CT in evaluation of systemic therapy response in prostate cancer

Purpose: To investigate the therapy response criteria for PSMA based PET/CT that published by EAU and EANM in 2020 by comparing with alterations of serum PSA values and determine the factors affecting therapy response evaluation with PSMA based PET/CT. Material and Method: A hundred [68Ga]Ga-PSMA-11 PET/CT scan that were acquired before and after therapy of consecutive 50 patients who received systemical antiandrogenic, chemotherapeutic or radionuclide therapy for prostate adenocarcinoma and were referred to Cukurova University Balcali Hospital Nuclear Medicine Department were evaluated retrospectively according to the published response criteria. The results of scans were compared with alteration of serum PSA values. An increase of % 25 and above of serum PSA level was accepted as biochemical progression, a decrease of % 50 or more or below 2 ng/ml as biochemical regression and as biochemical stable disease for between this range. The concordance between PET/CT results and serum PSA values was evaluated statistically with Gamma coefficient. The datas such as received therapies and castration resistance status were compared statistically between concordant and discordant group. In addition, the correlation between alterations of SUV values of lesion sites and serum PSA values were compared statistically. Results: A high concordance was found between [68Ga]Ga-PSMA-11 PET/CT results and serum PSA values and 0,84 of Gamma coefficient was obtained. Between concordant and discordant group, statistically significant difference was not found in terms of received therapies and castration resistance status. Statistically significant low correlation was found between serum PSA changes and prostate SUV values, and statistically significant moderate correlation was found metastatic lymph node and bone SUVmax values. Conclusion: The therapy response evaluation of PSMA PET/CT according to the published criteria shows high concordance with serum PSA values without being affected by received therapies or castration resistance. This criteria can be used with contribution of serum PSA values in therapy response of prostate cancer according to the our results and the literature datas.