The Application of ⁶⁸Ga-Somatostatin Analog and ¹⁸F-FDG PET/CT for Bone Metastasis from Neuroendocrine Tumors

Abstract

<b><i>Introduction:</i></b> Aims of the study were to assess the differences in the diagnostic efficacy of ⁶⁸Ga-somatostatin receptor analogs (⁶⁸Ga-SSAs) and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) for detecting bone metastases in neuroendocrine neoplasm (NEN) and to analyze the correlation between imaging features and clinical features of BMs. <b><i>Methods:</i></b> We retrospectively analyzed the clinical and imaging data of 213 NEN patients who underwent ⁶⁸Ga-SSA PET/CT and were finally diagnosed as BMs by pathology or follow-up. Of those, 103 patients underwent ¹⁸F-FDG PET/CT within 7 days after ⁶⁸Ga-SSA PET/CT. <b><i>Result:</i></b> The BM detection rate of ⁶⁸Ga-SSA PET/CT was higher than ¹⁸F-FDG PET/CT (86.4% vs. 66.0%, <i>p</i> = 0.02) in 103 patients with dual scanning. Meanwhile, the number of positive lesions in ⁶⁸Ga-SSA PET/CT was significantly more than in ¹⁸F-FDG PET/CT (3.37 ± 1.95 vs. 2.23 ± 2.16, <i>t</i> = 4.137, <i>p</i> &lt; 0.001). Most bone metastasis lesions presented as osteogenic change in CT (55.4%, 118/213). Concerning the primary tumor, the most frequent were of pancreatic origin (26.3%, 56/213), followed by rectal origin (22.5%, 48/213), thymic origin in 33 cases (15.5%), pulmonary origin in 29 cases (13.6%), paraganglioma in 20 cases (9.4%). The efficiency of ⁶⁸Ga-SSA PET/CT to detect BMs was significantly correlated with the primary site (<i>p</i> = 0.02), with thymic carcinoid BMs being the most difficult to detect, and the positive rate was only 60.6% (20/33). However, ¹⁸F-FDG PET/CT positive rate was 76.92% (10/13) in thymic carcinoid BMs. In addition, the BMs of 7 patients in this study were detected by ⁶⁸Ga-SSA PET earlier than CT for 4.57 months (range: 2–10 months). <b><i>Conclusion:</i></b> ⁶⁸Ga-SSA PET/CT has higher sensitivity for detecting the BMs of NEN than ¹⁸F-FDG and detects the BM earlier than CT. Moreover, ¹⁸F-FDG PET/CT should be a complement for diagnosing the BMs of thymic carcinoids.