The Role of Ga-68-DOTATATE PET in Patients with Neuroendocrine Tumors and Negative or Equivocal Findings on In-111-DTPA-Octreotide Scintigraphy

In-111-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 Ga-68-DOTATATE PET in a selected group of patients with negative or weakly positive findings on In-111-DTPA-octreotide scintigraphy to determine whether Ga-68-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 In-111-DTPA-octreotide scintigraphy underwent Ga-68-DOTATATE PET. Findings were compared using a region-by-region analysis. All findings were verified with CT or MRI. After Ga-68-DOTATATE PET, all cases were reviewed to determine whether the Ga-68-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. Ga-68-DOTATATE PET was positive in 41 of these 47 patients (87.2%). No false-positive lesions were identified. Ga-68-DOTATATE PET detected 168 of the 226 lesions (74.3%) that were identified with cross-sectional imaging. Ga-68-DOTATATE PET identified significantly more lesions than In-111-DTPA-octreotide scintigraphy (P < 0.001). There was no correlation between Ga-68-DOTATATE uptake and histologic grade of neuroendocrine tumors. Ga-68-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 In-111-DTPA-octreotide findings, Ga-68-DOTATATE PET identifies additional lesions and may alter management in most cases.