The aim of this study was to evaluate the diagnostic value of a new somatostatin analog, 68 Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N9,N$,N$9-tetraacetic acid-D-Phe 1 -Tyr 3 -octreotide ( 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 99m Tc-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 significantly higher detection rate compared with conventional somatostatin receptor scintigraphy and diagnostic CT with clinical impact in a considerable number of patients.

The GS and PSA level correlated with the intensity of tracer accumulation in the primary tumours of PC patients on Ga-PSMA-11 PET/CT. As PC tumours with GS 6+7 and patients with PSA values ≤10 ng/ml showed significantly lowerGa-PSMA-11 uptake, Ga-PSMA-11 PET/CT should be preferentially applied for primary staging of PC in patients with GS>7 or PSA levels ≥10 ng/ml.

The great potential of (68)Ga-PSMA PET/CT in patients with rPCa and BR was confirmed. PSA and PSAdt were valuable predictors of pathological (68)Ga-PSMA PET/CT findings.

68 Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N9,N99,N999-tetraacetic acid-D-Phe 1 -Tyr 3 -octreotide (DOTA-TOC) PET has proven its usefulness in the diagnosis of patients with neuroendocrine tumors. Radionuclide therapy ( 90 Y-DOTA-TOC or 177 Lu-DOTA-octreotate) is a choice of treatment that also requires an accurate diagnostic modality for early evaluation of treatment response. Our study compared 68 Ga-DOTA-TOC PET with CT or MRI using the Response Evaluation Criteria in Solid Tumors. Furthermore, standardized uptake values (SUVs) were calculated and compared with treatment outcome. Methods: Forty-six patients (29 men, 17 women; age range, 34-84 y) with advanced neuroendocrine tumors were investigated before and after 2-7 cycles of radionuclide therapy. Long-acting somatostatin analogs were not applied for at least 6 wk preceding the follow-up. Data were acquired with a dedicated PET scanner. Emission image sets were acquired at 90-100 min after injection. 68 Ga-DOTA-TOC PET images were visually interpreted by 2 experienced nuclear medicine physicians. For comparison, multislice helical CT scans and 1.5-T MRI scans were obtained. Attenuation-corrected PET images were used to determine SUVs. Repeated CT evaluation and other imaging modalities, for example, 18 F-FDG, were used as the reference standard. Results: According to the reference standard, 68 Ga-DOTA-TOC PET and CT showed a concordant result in 32 patients (70%). In the remaining 14 patients (30%), discrepancies were observed, with a final outcome of progressive disease in 9 patients and remission in 5 patients. 68 Ga-DOTA-TOC PET was correct in 10 patients (21.7%), including 5 patients with progressive disease. In these patients, metastatic spread was detected with the follow-up whole-body PET but was missed when concomitant CT was used. On the other hand, CT confirmed small pulmonary metastases not detected on 68 Ga-DOTA-TOC in 1 patient and progressive liver disease not detected on 68 Ga-DOTA-TOC in 3 patients. Quantitative SUV analysis of individual tumor lesions showed a large range of variability. Conclusion: 68 Ga-DOTA-TOC PET shows no advantage over conventional anatomic imaging for assessing response to therapy when all CT information obtained during follow-up is compared. Only the development of new metastases during therapy was detected earlier in some cases when whole-body PET was used. SUV analysis of individual lesions is of no additional value in predicting individual responses to therapy.

Somatostatin receptor scintigraphy is an accurate imaging modality for the diagnosis of neuroendocrine tumor. Because detection of distant metastases has a major impact on treatment, early diagnosis of metastatic spread is of great importance. So far, no standard procedure has become established for the early diagnosis of bone metastases from neuroendocrine tumor. We compared the diagnostic value of CT with that of the novel somatostatin analog 68 Ga-1,4,7,10-tetraazacyclododecane-N,N9,N$,N999-tetraacetic acid-D-Phe 1 -Tyr 3 -octreotide ( 68 Ga-DOTATOC) in the detection of such metastases. Methods: Fifty-one patients (22 women and 29 men; age range, 32-87 y) with histologically verified neuroendocrine tumor were included in this study. PET scans were fused with CT scans using a vacuum fixation device. 18 F-NaF or 99m Tc-dicarboxypropane diphosphonate bone scans or clinical follow-up served as the reference standard. Results: Twelve of the 51 patients had no evidence of bone metastases on any of the available imaging modalities, and 37 patients had 68 Ga-DOTATOC PET results true-positive for bone metastases. 68 Ga-DOTATOC PET results were true-negative for 12 patients, false-positive for one, and false-negative for another, resulting in a sensitivity of 97% and a specificity of 92%. 68 Ga-DOTATOC PET detected bone metastases at a significantly higher rate than did CT (P , 0.001). Furthermore, conventional bone scans confirmed the results of somatostatin receptor PET but did not reveal additional tumors in any patients. Conclusion: 68 Ga-DOTATOC PET is a reliable, novel method for the early detection of bone metastases in patients with neuroendocrine tumor. Our results show that CT and conventional bone scintigraphy are less accurate than 68 Ga-DOTATOC PET in the primary staging or restaging of neuroendocrine tumor.