Detection of Bone Metastases by 68Ga-DOTA-SSAs and 18F-FDG PET/CT: A Two-Center Head-to-Head Study of Gastroenteropancreatic Neuroendocrine Neoplasms

Purpose. This study aimed to assess the efficacy of dual-tracer [Ga-68-DOTA-somatostatin receptor analogs (SSAs) and F-18-fluorodeoxyglucose (FDG)] positron emission tomography/computed tomography (PET/CT) imaging for detecting bone metastases (BMs) in patients with gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). Methods. We retrospectively enrolled 74 GEP-NEN patients with BMs from two centers, who underwent dual-tracer PET/CT from January 2014 to March 2021. We compared and analyzed effectiveness of the dual PET/CT imaging techniques on the BMs, based on F-18-FDG and Ga-68-DOTA-SSAs. Specifically, we analyzed the imaging results using chi(2) tests for classification variables, paired-sample tests for number of BMs, Wilcoxon's signed rank test for number of lesions, and the Kruskal-Wallis test for standard uptake value (SUV) ratio comparison. The correlation of dual-tracer SUVmax with Ki-67 index was analyzed by Spearman's correlation coefficient. Results. The detection efficiencies of dual-tracer PET/CT imaging in patients with different pathologies showed discordant for detecting liver metastases and BMs in group neuroendocrine tumor (NET) G3, Ga-68-DOTA-SSAs was better at detecting BMs for NET G3 (P=0.049 for SUVT/B and P=0.026 for the number of metastatic lesions). In addition, statistical significance was found among osteogenesis group, osteolysis group, and the no-change group (for bone SUVT/B value detected by F-18-FDG and Ki-67 index, osteogenesis group < osteolysis group; for bone SUVT/B detected by Ga-68-DOTA-SSAs, osteogenesis group > the no-change group). What is more, liver and bone SUVmax and Ki-67 index were positively correlated in F-18-FDG imaging (P < 0.001 for liver; P=0.002 for bone), and negatively correlated in Ga-68-DOTA-SSAs imaging (P < 0.001 for liver; P=0.039 for bone). Conclusions. Ga-68-DOTA-SSAs was superior to F-18-FDG for detecting BMs in NET G1/G2 (well and moderately differentiated NETs), as well as in NET G3 (poorly differentiated NETs). Relatively good differentiation was observed in the osteogenesis group. In addition, dual-tracer PET/CT imaging results were observably correlated with tumor differentiation.

Automated summary

This study assessed the efficacy of dual-tracer PET/CT imaging for detecting bone metastases in patients with GEP-NENs. The results showed that Ga-68-DOTA-SSAs were superior to F-18-FDG for detecting bone metastases in both well/moderately differentiated and poorly differentiated NETs. The imaging results were also correlated with tumor differentiation.