Comparison of 18F-FDG and 68Ga-DOTA-NOC PET/CT on the diagnosis of G3 neuroendocrine neoplasm

Objective To investigate the clinical value of 18F-FDG PET/CT in diagnosing G3 NEN and compare it with 68Ga-DOTA-NOC PET/CT. Methods Twenty-three patients (12 males, 11 females; average age (63±12) years) diagnosed of NEN between January 2006 and November 2016 were retrospectively recruited in this study: 11 patients with gastroenteropancreatic NEN(GEP-NEN), 10 with G3 NEN in lungs, 1 with malignant pheochromocytoma and 1 with G3 NEN of unknown primary site. All patients underwent 18F-FDG PET/CT for staging and evaluation of biological behavior, and 9 of them also underwent 68Ga-DOTA-NOC PET/CT within 1 week. Image interpretation was analyzed by visual and semi-quantitative analysis, and SUVmax was calculated. Results All 23 cases showed positive results on 18F-FDG PET/CT (100%, 23/23), with primary tumor SUVmax 10.56±3.94. Compared with 18F-FDG PET/CT, the positive detection rate of 68Ga-DOTA-NOC PET/CT was lower (6/9 vs 9/9), with primary tumor SUVmax 14.24±10.00. There were 22 patients with distant metastasis. The most frequent metastatic sites associated with G3 NEN in lungs were lymph nodes and bones, while those with GEP-NEN were lymph nodes and the liver. In one patient with non-functional NEN, some metastatic lesions showed negative results on 18F-FDG PET/CT but positive results on 68Ga-DOTA-NOC PET/CT. Conclusions 18F-FDG PET/CT has higher diagnostic ability for G3 NEN and may serve as a useful tool for evaluating biological behavior of G3 NEN. 68Ga-DOTA-NOC PET/CT is valuable as a complementary diagnostic tool in a small proportion of high differentiated G3 NEN. Key words: Carcinoma, neuroendocrine; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose; Octreotide