68Ga-PSMA-HBED-CC uptake in cervical, coeliac and sacral ganglia as an important pitfall in prostate cancer PET imaging

The study aims to investigate the presence of physiological prostate-specific membrane antigen (PSMA)-ligand uptake on positron-emission-tomography (PET) in cervical, coeliac and sacral ganglia of the sympathetic trunk as a pitfall for lymph node metastases in prostate cancer imaging. Methods: 407 patients who underwent "Glu-NH-CO-NH-Lys" radio-labeled 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 computed tomography (CT)) were retrospectively analyzed. The number of PSMA PET-positive cervical, coeliac and sacral ganglia was determined and the configuration and maximum standardized uptake value (SUVmax) of each ganglion was measured. In addition, the configuration and SUVmax of adjacent lymph node metastases in the respective region (cervical, coeliac or sacral) were determined. Results: 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 coeliac ganglia, and in 183 (46%) patients in sacral ganglia. The PSMA-ligand uptake was highest in coeliac (mean SUVmax 2.9±0.8 vs. cervical (mean SUVmax 2.4±0.6) and sacral (mean SUVmax 1.7±0.5), both p<0.0001) ganglia. Intra-individually there was a statistically significant, but weak to moderate correlation between the PSMA-ligand uptake in cervical vs. coeliac ganglia (R=0.34, p<0.0001), cervical vs. sacral (R=0.52, p<0.0001) and coeliac vs. sacral (R=0.16, p<0.05). The PSMA-ligand uptake was significantly more intense in adjacent lymph node metastases compared to the respective ganglia (cervical: 18.0±16.2 vs. 2.4±0.6, p<0.0001; coeliac: 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 (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: 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 PSMA-ligand uptake is higher in coeliac ganglia compared to cervical or sacral ganglia and the level of PSMA-ligand uptake seems to be patient-related. For the differentiation between lymph node metastases and sympathetic ganglia both intensity of PSMA-ligand-uptake as well as exact localization and configuration of the respective lesion should be examined carefully.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2018 Jan 25 [Epub ahead of print]

Christoph Rischpler, Teresa Isabel Beck, Shozo Okamoto, Anna Melissa Schlitter, Karina Knorr, Markus Schwaiger, Jürgen Gschwend, Tobias Maurer, Philipp T Meyer, Matthias Eiber

Dept of Nuclear Medicine, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany, Germany., Department of Nuclear Medicine, Medical Center - University of Freiburg, Germany, Germany., Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, Japan, Japan., Institute of Pathology, Technical University Munich, Munich, Germany., Department of Urology, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany, Germany.