Correlations of the 68Ga-PSMA PET/CT derived primary prostate tumor PSMA expression parameters and metastatic patterns in patients with Gleason Score >7 prostate cancer.

Abstract

We aimed to investigate the correlations between the prostate specific membrane antigen (PSMA) expression parameters of the primary prostate tumor on gallium-68 (68Ga)-PSMA positron emission tomography/computed tomography (PET/CT) with metastatic patterns in patients with Gleason Score (GS) >7 prostate cancer (PCa). This study included 55 PCa patients who had 68Ga-PSMA PET/CT performed for staging. According to metastatic pattern, patients were divided into 3 groups as non-metastatic (N0M0), those with isolated pelvic lymph node metastasis (N1M0) and with distant metastasis (M1). The correlations between the primary tumor PSMA expression parameters such as maximum standardize uptake value (SUVmax), SUVmean, PSMA-TV (PSMA receptor expressing tumour volume), and TL-PSMA (total lesion PSMA receptor expression) on 68Ga-PSMA PET/CT imaging and metastatic patterns were investigated. There were 21, 9 and 25 patients in the N0M0, N1M0 and M1 groups, respectively. The PSMA-TV and TL-PSMA values were significantly higher in the N1M0 and the M1 patient groups compared to the N0M0 group, but there was no significant difference between the N1M0 and M1 groups. The primary tumor SUVmax and SUVmean values were not significantly different between the three groups. The optimal PSMA-TV cut-off value for metastasis was >8.07cm3 (AUC 0.86) with sensitivity of 76.5% and specificity 85.7%. The optimal TL-PSMA cut-off value for metastasis was >93 (AUC 0.74) with sensitivity of 64%, and specificity 100%. The PSMA-TV and TL-PSMA values are strong markers for metastasis prediction in patients with GS >7 PCa but no other PSMA expression parameters can distinguish between N1M0 and M1 groups.