Usefulness of PET/CT investigations with 68Ga-DOTATATE in neuroendocrine tumors in diagnosis of primary tumors

Objectives Somatostatin receptor scintigraphy is usual imaging modality for the diagnosis of neuroendocrine tumor(NET).Novel techniques PET/CT with 68Ga-DOTATATE open new diagnostic way in the diagnosis of patients with NET. Sensitivity of that techniques is depending on SSTR expression, but average range is 60-94%. In disseminated NET very important question is localizing of primary tumors. Resection of a carcinoid tumor localized to its primary site approaches a 100% survival rate. The aim of this study was to evaluate the diagnostic usefulness of a new somatostatin analog, 68Ga-DOTATATE, for PET/CT in patients with metastatic neuroendocrine carcinoma with unknown primary tumors.

Methods 267 patients with disseminated NET were examined. In that group 52 (19%) patients were referred for examination for localize primary tumor site (24 men, 28 women; age range, 20-74 y; mean age +/- SD, 50.4 +/- 12.1 y). PET imaging was performed on PET/CT scanner Biograph 64, 60-80 minutes post injection of 120-185 MBq 68Ga-DOTA-TATE.

Results 68Ga-DOTATATE revealed 42/52 (81 %) primary foci. 6 foci were localized in lungs, retrospective analysis of CT revealed small nodule in the lung 4-5 mm. 16 were observed in pancreas, only 2 were seen in CT. In intestine PET/CT revealed 18 primary tumors, 12 localized in small intestine, 6 in colon; in CT in small intestine polypus was seen only in 1 cases, in colon thicken of wall was seen in 2 cases. Additionally primary tumors were seen in stomach - 1 patient and in pelvis - 1 patient, both seen in CT. Neither PET/CT with 68Ga-DOTATATE nor CT with contrast media was (not) found primary tumors in 10/52 (19%).

Conclusions 68Ga-DOTATATE PET/CT is useful non-invasive technique in diagnosis of patients with NET in cases of unknown primary tumors. In our study 68Ga-DOTATATE PET/CT enable localized 80% primary tumors site