Gastroenteropancreatic neuroendocrine tumors (GEPNETs) are indolent neoplasms presenting unpredictable and unusual biologic behavior that causes many clinical challenges. Tumor size, existence of metastasis, and histopathologic classification remain incapable in terms of treatment decision and prognosis estimation. This study aimed to compare 68 Ga-DOTATATE and 18 F-FDG PET/CT in GEPNETs and to investigate the relation between the complementary PET/CT results and histopathologic findings in the management of therapy, particularly in intermediate-grade patients. Methods: The relation between complementary 68 Ga-DOTATATE and 18 F-FDG PET/CT results of 27 GEPNET patients (mean age, 56 y; age range, 33-79 y) and histopathologic findings was evaluated according to grade and localization using standardized maximum uptake values and Ki67 indices. Grade 2 (G2) patients were further evaluated in 2 groups as G2a (3%-9%) and G2b (10%-20%) according to Ki67 indices. Results: The sensitivity of 68 Ga-DOTATATE and 18 F-FDG PET/CT was 95% and 37%, respectively, and the positive predictive values were 93.8% and 36.2%, respectively. The sensitivity in detecting liver metastasis, lymph nodes, bone metastasis, and primary lesion was 95%, 95%, 90%, and 93% for 68 Ga-DOTATATE and 40%, 28%, 28%, and 75% for 18 F-FDG, respectively. Statistically significant differences were found between grades 1-2, 2a-2b, and 1-2b with respect to 68 Ga-DOTATATE PET/CT as well as between 1-2a and 1-2b with respect to 18 F-FDG PET/CT. However, no statistical differences were found between 1 and 2a (P . 0.05) for 68 Ga-DOTATATE and 2a and 2b (P 5 0.484) for 18 F-FDG. The impact of the combined 18 F-FDG and 68 Ga-DOTATATE PET/CT on the therapeutic decision was 59%. Conclusion: Combined 68 Ga-DOTATATE and 18 F-FDG PET/ CT is helpful in the individual therapeutic approach of GEPNETs and can overcome the shortcomings of histopathologic grading especially in intermediate-grade GEPNETs.

(68)Ga-DOTATATE has high T/B ratio with physiological biodistribution comparable to its counterparts. However, the presence of SSTRs in benign and malignant lesions unrelated to NET may be challenging in interpretation particularly where the physiological uptake is variable.

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Microbiological examination may be as useful as and less costly than other diagnostic procedures and is the only method which can guide the choice of antibiotic therapy.

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