Neuroendocrine Tumors: Comparison with Somatostatin Receptor Scintigraphy and CT

( 68 Ga-DOTA-TOC), for PET in patients with known or suspected neuroendocrine tumors. PET was compared with conventional scintigraphy and dedicated CT. Methods: Eighty-four patients (48 men, 36 women; age range, 28–79 y; mean age 6 SD, 58.2 6 12.2 y) were prospectively studied. For analysis, patients were divided into 3 groups: detection of unknown primary tumor in the presence of clinical or biochemical suspicion of neuroendocrine malignancy (n 5 13 patients), initial tumor staging (n 5 36 patients), and follow-up after therapy (n 5 35 patients). Each patient received 100–150 MBq 68 Ga-DOTA-TOC. Imaging results of PET were compared with 99mTc-labeled hydrazinonicotinyl-Tyr 3 -octreotide ( 99m Tc-HYNIC-TOC) and 111 In-DOTA-TOC. CT was also performed on every patient using a multidetector scanner. Each imaging modality was interpreted separately by observers who were unaware of imaging findings before comparison with PET. The gold standard for defining true-positive (TP), true-negative (TN), false-positive (FP), and false-negative (FN) results was based on all available histologic, imaging, and follow-up findings. Results: PET was TP in 69 patients, TN in 12 patients, FP in 1 patient, and FN in 2 patients, indicating a sensitivity of 97%, a specificity of 92%, and an accuracy of 96%. The FP finding was caused by enhanced tracer accumulation in the pancreatic head, and the FN results were obtained in patients with a tumor of the gastrointestinal tract displaying liver metastases. 68 Ga-DOTA-TOC showed higher diagnostic efficacy compared with SPECT (TP in 37 patients, TN in 12 patients, FP in 1 patient, and FN in 34 patients) and diagnostic CT (TP in 41 patients, TN in 12 patients, FP in 5 patients, and FN in 26 patients). This difference was of statistical significance (P , 0.001). However, the combined use of PET and CT showed the highest overall accuracy. Conclusion: 68 Ga-DOTA-TOC PET shows a