⁶⁸Ga-PSMA-HBED-CC Uptake in Cervical, Celiac, and Sacral Ganglia as an Important Pitfall in Prostate Cancer PET Imaging

Abstract

The study aims to investigate the presence of physiologic prostate-specific membrane antigen (⁶⁸Ga-PSMA)-ligand uptake on PET in cervical, celiac, and sacral ganglia of the sympathetic trunk as a pitfall for lymph node metastases in prostate cancer imaging. Methods: Four hundred seven patients who underwent Glu-NH-CO-NH-Lys radiolabeled with ⁶⁸Ga-gallium N,N-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N-diacetic acid (⁶⁸Ga-PSMA-HBED-CC) PET (combined with a diagnostic CT) were retrospectively analyzed. The number of ⁶⁸Ga-PSMA PET–positive cervical, celiac, and sacral ganglia was determined, and the configuration and SUV_max of each ganglion were measured. In addition, the configuration and SUV_max of adjacent lymph node metastases in the respective region (cervical, celiac, or sacral) were determined. Results: ⁶⁸Ga-PSMA-ligand uptake above background was detected in 401 (98.5%) patients in any peripheral ganglia, in 369 (92%) patients in cervical ganglia, in 363 (89%) patients in celiac ganglia, and in 183 (46%) patients in sacral ganglia. The ⁶⁸Ga-PSMA-ligand uptake was highest in celiac (mean SUV_max, 2.9 ± 0.8 vs. cervical mean SUV_max, 2.4 ± 0.6) and sacral (mean SUV_max 1.7 ± 0.5; both P < 0.0001) ganglia. Intraindividually there was a statistically significant but weak to moderate correlation between the ⁶⁸Ga-PSMA-ligand uptake in cervical versus celiac ganglia (R = 0.34, P < 0.0001), cervical versus sacral (R = 0.52, P < 0.0001), and celiac versus sacral (R = 0.16, P < 0.05). The ⁶⁸Ga-PSMA-ligand uptake was significantly more intense in adjacent lymph node metastases than the respective ganglia (cervical: 18.0 ± 16.2 vs. 2.4 ± 0.6, P < 0.0001; celiac: 13.5 ± 12.3 vs. 2.9 ± 0.8, P < 0.0001; sacral: 13.4 ± 11.6 vs. 1.7 ± 0.5, P < 0.0001). Furthermore, ganglia predominantly exhibit a band-shaped configuration (71.2%), followed by a teardrop (26.8%) and only rarely a nodular configuration (2.0%). Conversely, lymph node metastases are only rarely band-shaped (1.1%), but more often show teardrop (40.3%) or nodular appearance (58.6%) (P < 0.00001). Conclusion: ⁶⁸Ga-PSMA-ligand uptake in ganglia along the sympathetic trunk as assessed by ⁶⁸Ga-PSMA-HBED-CC PET represents an important pitfall in prostate cancer PET imaging. The ⁶⁸Ga-PSMA-ligand uptake is higher in celiac ganglia than cervical or sacral ganglia, and the level of ⁶⁸Ga-PSMA-ligand uptake seems to be patient-related. For the differentiation between lymph node metastases and sympathetic ganglia, both intensity of ⁶⁸Ga-PSMA-ligand uptake and exact localization and configuration of the respective lesion should be examined carefully.