Role of 68Ga-PSMA PET/CT parameters in treatment evaluation and survival prediction in prostate cancer patients compared with biochemical response assessment.

OBJECTIVE In this study, we aimed to evaluate the concordance of biochemical treatment response with gallium-68-prostate specific membrane antigen (68Ga-PSMA) positron emission tomography/computed tomography (PET/CT) treatment response in prostate cancer (PCa) and investigate their prognostic effects on survival. MATERIALS AND METHODS One hundred and fifty-onepatients with PCa, who underwent 68Ga-PSMA PET/CT imaging in our clinic between May 2016 and December 2019, were on treatment, and had pre-treatment and post-treatment imaging studies were included in our study. The treatment patients received and prostate-specific antigen (PSA) levels at the time of PET/CT imaging were recorded. Pre- and post-treatment whole-body metabolic tumor volume (MTVw), whole-body total lesion PSMA (TLPw), percent change in PSA (ΔPSA), ΔMTV, and ΔTLP values were calculated in all patients. Survival time of all patients was measured from the time of initial PET imaging. RESULTS Median age of patients included in our study was 71 years (range: 51-88). When ΔPSA response and ΔTLP response were evaluated together (r: 0.71, P<0.001 and k: 0.541, P<0.001), statistically significance strong correlation and moderate concordance was observed. ΔPSA response and ΔMTV treatment response had statistically significant moderate correlation and moderate concordance (r: 0.66, P<0.01 and k: 0.454, P<0.001, significantly). Between ΔPSA response and ΔTLP and ΔMTV response had stronger correlation and higher concordance when PSA levels were above 10. Multivariate analyses using multiple Cox regression analysis revealed MTVw1 and ΔMTV parameters to be independent prognostic factors for mortality (P:0.003 and P:0.001, respectively). CONCLUSION We observed that biochemical response and whole-body volumetric 68Ga-PSMA PET/CT parameter response showed correlation and concordance in all groups with PCa, which was more significant when PSA level was ≥10ng/mL. MTVw1 and ΔMTV parameters obtained via 68Ga-PSMA PET/CT were independent prognostic factors for mortality in PCa. Gallium-68-PSMA PET/CT is a valuable imaging technique for diagnostic purposes as well as follow-up and prognostic evaluation.