111 In-diethylenetriaminepentaacetic acid (DTPA)-octreotide scintigraphy is currently the nuclear medicine imaging modality of choice for identifying neuroendocrine tumors. However, there are cohorts of patients in whom scintigraphy findings are negative or equivocal. We evaluated the role of 68 Ga-DOTATATE PET in a selected group of patients with negative or weakly positive findings on 111 In-DTPA-octreotide scintigraphy to determine whether 68 Ga-DOTATATE PET is able to detect additional disease and, if so, whether patient management is altered. Methods: Fifty-one patients with a histologically confirmed diagnosis of neuroendocrine tumors were included. Of the 51 patients, 35 who were negative and 16 equivocal for uptake on 111 In-DTPA-octreotide scintigraphy underwent 68 Ga-DOTATATE PET. Findings were compared using a region-by-region analysis. All findings were verified with CT or MRI. After 68 Ga-DOTATATE PET, all cases were reviewed to determine whether the 68 Ga-DOTATATE PET findings resulted in any alteration in management, in terms of suitability for peptide receptor therapy, somatostatin analogs, and surgery. Results: Of the 51 patients, 47 had evidence of disease on cross-sectional imaging or biochemically. 68 Ga-DOTATATE PET was positive in 41 of these 47 patients (87.2%). No falsepositive lesions were identified. 68 Ga-DOTATATE PET detected 168 of the 226 lesions (74.3%) that were identified with crosssectional imaging. 68 Ga-DOTATATE PET identified significantly more lesions than 111 In-DTPA-octreotide scintigraphy (P , 0.001). There was no correlation between 68 Ga-DOTATATE uptake and histologic grade of neuroendocrine tumors. 68 Ga-DOTATATE imaging changed management in 36 patients (70.6%), who were subsequently deemed suitable for peptide receptor-targeted therapy. Conclusion: In patients with negative or equivocal 111 In-DTPA-octreotide findings, 68 Ga-DOTATATE PET identifies additional lesions and may alter management in most cases.

Synchronous malignant neoplasms in a single patient are well documented in the literature. It is also recognized that there is increasing incidence of synchronous non-neuroendocrine neoplasm in patients with neuroendocrine tumor (NET). We present a case, of a patient with synchronous colorectal cancer and pancreatic NET, both cancers presenting with liver metastasis. By using 18F-FDG PET and 68Ga-DOTATATE PET imaging, we showed 2 different tumor types within the liver, which was subsequently confirmed on liver biopsy. This case report shows the utility of molecular imaging using different PET peptides. These newer modalities are useful in understanding the biology of the NET and in determining the best patient management.