PSMA-1007 Uptake in Ganglia of the Sympathetic Trunk and Its Intra-individual Reproducibility

Aim/purpose: ¹⁸F-labeled PSMA ligands offer various advantages as PET tracers over ⁶⁸Ga-labeled PSMA counterparts. Especially, an improved spatial resolution leads to improved detection rates of smaller prostate Cancer (PCa) lesions. However, physiological PSMA uptake of ganglia of the sympathetic trunk can be quickly misinterpreted as possible PSMA-positive lymph node metastases. The aim of this retrospective study is to investigate [¹⁸F]PSMA-1007 uptake and its intra-individual reproducibility in ganglia of the sympathetic trunk.

Methods: We retrospectively included 28 consecutive patients (median age 69 ± 9 with a range of 49-90) with biochemical recurrence of PCa who underwent [¹⁸F]PSMA-1007 PET/CT scan and, accordingly, a follow-up examination between August 2018 and August 2021. Cervical, coeliac, and sacral ganglia were identified on the iterative PET reconstructions and correlated with CT component. Tracer uptake of ganglia was determined by measuring SUV_max and SUV_mean values. Anatomical position of the ganglia in relation to adjacent vertebral bodies were noted. Statistical analyses were conducted using two-way repeated measures ANOVA and descriptive statistics.

Results: The highest [¹⁸F]PSMA-1007 uptake was found in coeliac ganglia followed by cervical and sacral ganglia. The SUV_max in coeliac ganglia was 3.13 ± 0.85 (follow-up scan 3.11 ± 0.93), in cervical ganglia 2.73 ± 0.69 (follow-up scan 2.67 ± 0.74), and in sacral ganglia 1.67 ± 0.50 (follow-up scan 1.64 ± 0.52). The SUV_mean in coeliac ganglia was 2.28 ± 0.64 (follow-up scan 2.28 ± 0.66), in cervical ganglia 1.62 ± 0.43 (follow-up scan 1.61 ± 0.43) and in sacral ganglia 1.15 ± 0.33 (follow-up scan 1.12 ± 0.34). In a given ganglion station, there was no statistically significant difference of SUV_max or SUV_mean values between baseline and follow-up scans.

Conclusions: The first systematically described physiological [¹⁸F]PSMA-1007 uptake in ganglia of the sympathetic trunk showed a low variability of SUV_max or SUV_mean and a good intra-individual reproducibility of [¹⁸F]PSMA-1007 uptake in follow-up scans. These findings might improve and guide the differentiation of ganglia from possible malignant lesions.

F-18 PSMA; Ganglia; PET; PSMA-1007; Prostate cancer; Sympathetic trunk.