Somatostatin receptor imaging combining with ¹⁸F-FDG PET/CT for the evaluation of biologic behavior in gastroenteropancreatic neuroendocrine tumors

Objectives: The aim of this study is to validate the clinical value of ⁶⁸Ga-DOTA-NOC combining with¹⁸F-FDG PET/CT for the evaluation of biologic behavior in GEP-NENs.

Methods: Seventy eight patients with G1-2 GEP-NETs and 23 patients with G3 NEC were enrolled in this prospective study. All patients underwent ⁶⁸Ga-DOTA-NOC and ¹⁸F-FDG PET/CT in one week, which is utilized for staging and evaluation of biologic behavior. Image interpretation was analyzed by visual analysis, tumor uptake was expressed as standard uptake value (SUV). The final diagnosis was confirmed by histopathology, G staging based on Ki67 proliferation index and mitosis was also confirmed.

Results: Results Three patterns (mismatch, reverse mismatch and match) could be observed between ⁶⁸Ga-DOTA-NOC and ¹⁸F-FDG PET/CT. Patients in G1 presented with mismatch style, but in G2 some patients presented with reverse mismatch and match, patients in G3 presented reverse mismatch. However, overlap was existed in different staging, mainly on G2. All G3 cases are ¹⁸F-FDG-avid, not only in primary lesions but metastasis, SUV_max of the primary lesion and metastasis in G1-2 was 3.47±1.78, 3.89±2.67,respectively. Whereas ⁶⁸Ga-DOTA-NOC PET/CT showed mild or moderate uptake in 20 patients with G3 NEC, no significant uptake in 3 PTS. SUV_max of primary lesion and metastasis in G1-2 was 14.57±8.78, 15.68±7.45 respectively. In G3 NEC, SUV_max of ⁶⁸Ga-DOTA-NOC was 10.24±7.87, whereas that of ¹⁸F-FDG was 10.56±3.94.

Conclusion: ⁶⁸Ga-DOTA-NOC and ¹⁸F-FDG PET/CT serve as useful tools for the evaluation of biologic behavior in GEP-NENs, which will contribute to select treatment strategy, ⁶⁸Ga-DOTA-NOC PET/CT is also valuable for the identification of high differentiated G3 NET from G3 NEC. Research Support: