Diagnostic Efficacy of ⁶⁸ Gallium-PSMA Positron Emission Tomography Compared to Conventional Imaging for Lymph Node Staging of 130 Consecutive Patients with Intermediate to High Risk Prostate Cancer

Abstract

In patients with intermediate to high risk prostate cancer preoperative lymph node staging with (68)Ga-PSMA-PET proved to be superior to standard routine imaging. Thus it has the potential to replace current standard imaging for this indication if confirmed by prospective studies.

PSMA Ligands for PET Imaging of Prostate Cancer

“…For example, in a retrospective analysis of 130 patients with primary intermediate-to high-risk PC using templatebased pelvic histopathology as a reference, 68 Ga-PSMA-11 PET performed significantly better than morphologic imaging for N staging both on a patient and a template basis (P 5 0.002 and , 0.001, respectively). On template-based analysis, the sensitivity, specificity, and accuracy were 68.3%, 99.1%, and 95.2% for 68 Ga-PSMA-11 PET and 27.3%, 97.1%, and 87.6% for morphologic imaging, respectively (21). Similar results on the diagnostic efficacy of PSMA ligand PET for the detection of nodal metastases were obtained in other studies (47,49).…”

“…The excellent specificity of PSMA ligands, especially for lymph node metastases, was demonstrated in several studies (21,39,46,(83)(84)(85). Therefore, any focal uptake of the PSMA ligand higher than the surrounding background uptake in morphologically visible lesions and not associated with physiologic uptake should be considered suggestive.…”

“…In a recent investigation, at least one celiac ganglion with increased PSMA ligand uptake mimicking retroperitoneal lymph node disease was found in 89% of patients undergoing 68 Ga-PSMA-11 PET/ CT examinations (96). Another important limitation is the absence of PSMA overexpression in the primary tumor or its metastases in up to 10% of patients with primary PC or (as mentioned above) decreased PSMA expression in advanced disease (21). Side-by-side interpretation of the diagnostic CT scan as part of the PSMA ligand PET/CT examination is important.…”

“…In detecting sites of nodal or bone involvement in preoperative patients, cross-sectional imaging has shown a limited pooled sensitivity and specificity of 42% and 82%, respectively, for CT and 39% and 82%, respectively, for MRI (3), as up to 80% of lymph node metastases in PC are harbored in normal-sized lymph nodes (2). Several studies showed a clear superiority of PSMA ligand PET/CT over standard-of-care imaging (CT, MRI, or bone scanning) (21,(46)(47)(48)(49). For example, in a retrospective analysis of 130 patients with primary intermediate-to high-risk PC using templatebased pelvic histopathology as a reference, 68 Ga-PSMA-11 PET performed significantly better than morphologic imaging for N staging both on a patient and a template basis (P 5 0.002 and , 0.001, respectively).…”

“…PSMA is a transmembrane protein that is highly overexpressed (100-to 1,000-fold) on almost all PC tumors (16)(17)(18)(19). Only 5%-10% of primary PC lesions have been shown to be PSMA-negative (20,21). PSMA expression levels increase with higher tumor stage and grade (16,18,22).…”