Confirmation of PSMA expression measured on [68Ga]Ga-PSMA PET/CT by immunohistochemistry in prostate adenocarcinoma

Our aim is to determine the accuracy of [68Ga]Ga-PSMA PET/CT in showing PSMA expression in primary prostate cancer and to investigate the relationship between SUVmax and immunohistochemical PSMA expression, Gleason score, and PSA value.

We retrospectively analyzed 66 male patients who were diagnosed with primary prostate adenocarcinoma, underwent pre-treatment [68Ga]Ga-PSMA PET/CT examination for staging, and performed radical prostatectomy between March 2018-August 2020. Immunohistochemical staining was applied to the radical prostatectomy specimens of all patients to detect PSMA expression. The results were evaluated as an immunoreactive score (IRS) and a modified IRS was obtained. Gleason score groups and prostate-specific antigen (PSA) serum values of the patients were obtained from the patient files.

The high SUVmax of primary prostate tumors was significantly correlated with a high modified IRS score (score 2; 3), high PSA value, high Gleason score, and metastasis. In correlation analysis, a positive correlation was found between SUVmax and PSA value and modified IRS score (r = 0.69, p = 0.001; r = 0.39, p = 0.001). In addition, there was a statistically significant weak correlation between PSA serum concentration and modified IRS scores (r = 0.267; p = 0.03). In regression analysis, the percentage of positive cells had a statistically significant and increasing effect on SUVmax (p = 0.031; std beta = 0.268; 95% CI = 0.231-4.596).

In prostate adenocarcinoma, SUVmax of the primary tumor in [68Ga]Ga-PSMA PET/CT correlates with immunohistochemical PSMA expression. In addition, high SUVmax is associated with markers of poor prognoses, such as high PSMA expression, PSA value, and Gleason score.