Correlations of 68Ga-PSMA PET/CT in the initial staging of prostate cancer patients

Objective: The aim of this study was to evaluate the correlations between the different risk groups of prostate cancer (PCa) regarding the presence of metastasis and the gallium-68 prostate specific membrane antigen (Ga-68-PSMA) uptake patterns in the prostate gland. Materials and Methods: One hundred thirty nine patients with newly diagnosed, untreated PCa who underwent Ga-68-PSMA PET/CT imaging for staging between July 2017 and March 2019 were enrolled in this retrospective study. Maximum standardized uptake values (SUVmax) were determined by manually placing the region of interest to the primary tumor in the prostate gland. Patients were divided into groups according to their prostate-specific antigen (PSA) values, International Society of Urological Pathology (ISUP) grade groups, Gleason Scores (GS), D'Amico risk stratification criteria and the presence of metastasis. Mann Whitney U test was used in the comparison of two groups of data. In multivariate analysis, logistic regression was used to determine independent predictors for the presence of metastasis. Results: There were statistically significant differences between D'Amico risk groups in terms of prostate SUVmax levels. The SUVmax levels of the patients in the high risk group were significantly higher than the SUVmax levels of the patients in the low-medium risk groups (P<0.001). Maximum standardized uptake value levels of the patients with PSA level 20ng/mL and above were significantly higher than those with PSA level below 20ng/mL (P<0.001). The metastatic rate of patients with Ga-68-PSMA uptake on two lobes of the prostate gland was significantly higher (42.6%) than the metastatic rate of patients with( 68)Ga-PSMA uptake on only one lobe (7.9%) (P<0.001). The median SUVmax of tumours in patients with metastasis was statistically significantly higher than in patients with no metastasis. In multivariate analysis; bilobar involvement, PSA value 20ng/mL, prostate SUVmax value 8.6 and GS 8 were determined as independent predictors for the presence of metastasis. Conclusion: The strong correlation between PSA values and/or Gleason score/Grade and SUVmax values suggests that the SUVmax value of the prostate gland might be a valuable determinant in risk classifications.