Niraj Naswa

Gallium-68-DOTA-NOC PET/CT of Patients With Gastroenteropancreatic Neuroendocrine Tumors: A Prospective Single-Center Study

OBJECTIVE The objective of this study was to evaluate the role of (68)Ga-labeled [1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid]-1-NaI(3)-octreotide (DOTA-NOC) PET/CT in the diagnosis and management of gastroenteropancreatic neuroendocrine tumors (NETs). SUBJECTS AND METHODS One hundred nine patients (median age, 50 years) with gastroenteropancreatic NETs underwent (68)Ga-DOTA-NOC PET/CT. PET/CT was performed after injection of 132-222 MBq (4-6 mCi) of (68)Ga-DOTA-NOC. Images were evaluated by two experienced nuclear medicine physicians both qualitatively as well as quantitatively (maximum standardized uptake value [SUV(max)]). Results of PET/CT were compared with the results of conventional imaging. Histopathology results, when available, and follow-up PET/CT or conventional imaging with biochemical markers were considered to be the reference standards. RESULTS Gallium-68-DOTA-NOC PET/CT showed sensitivity and specificity of 78.3% and 92.5%, respectively, for primary tumor and 97.4% and 100% for metastases. It was better than a conventional imaging modality for the detection of both primary tumor (p < 0.001) and metastases (p < 0.0001). It changed the management strategy in 21 patients (19%) and supported management decisions in 32 patients (29%). CONCLUSION Gallium-68-DOTA-NOC PET/CT appears to be a highly sensitive and specific modality for the detection of gastroenteropancreatic NET. It is better than conventional imaging for the evaluation of gastroenteropancreatic NETs and can have a significant impact on patient management.

Role of (68)Ga-DOTATOC PET-CT in the diagnosis and staging of pancreatic neuroendocrine tumours.

ObjectiveThe objective of the present study was to evaluate the role of 68Ga-DOTA(0)-Phe(1)-Tyr(3)-octreotide (68Ga-DOTATOC) positron emission tomography computed tomography (PET-CT) for detection and staging of pancreatic neuroendocrine tumours (NETs).MethodsTwenty patients with clinically suspected and/or histopathologically proven pancreatic NET underwent 68Ga-DOTATOC PET-CT imaging for staging and /or localisation of primary lesion. They also underwent contrast enhanced CT (CECT) and 8 patients underwent 18F-FDG PET-CT. SUVmax of primary and metastatic lesions were measured. Results were verified with histopathology for primary tumour and with clinical follow up/MRI and /or biopsy for metastatic disease. Results of 68Ga-DOTATOC PET-CT were compared to CECT and 18F-FDG PET-CT.Results68Ga-DOTATOC PET-CT correctly localised primary in all 20, CECT in 15 and 18F-FDG PET-CT in 2 patients. 68Ga-DOTATOC PET-CT demonstrated metastases in 13 patients, CECT in 7 and 18F-FDG PET-CT in 2. 68Ga-DOTATOC PET-CT emerged as the best investigation with 100% sensitivity and PPV for detecting primary tumour and metastatic disease. The detection rate of CECT was lower than 68Ga-DOTATOC PET-CT, both for primary tumour (20vs.15) or metastatic disease (13vs.7). 18F-FDG PET-CT performed poorly for primary and metastasis.ConclusionGa-DOTATOC PET-CT is a very useful imaging investigation for diagnosing and staging pancreatic NET.

68Ga-DOTANOC PET/CT for Baseline Evaluation of Patients with Head and Neck Paraganglioma

The purpose of this study was to evaluate the role of 68Ga-labeled DOTANOC PET/CT for baseline evaluation of patients with head and neck paragangliomas (HNPs). Methods: The data for 26 patients (mean age ± SD, 34.3 ± 10.4 y; 50% men) with known or suspected HNPs who underwent 68Ga-DOTANOC PET/CT for staging were retrospectively analyzed. PET/CT was performed after intravenous injection of 132–222 MBq of 68Ga-DOTANOC. The images were evaluated by 2 experienced nuclear medicine physicians in consensus, both qualitatively and quantitatively. The PET/CT findings were grouped as HNPs, paraganglioma at other sites (non-HNPs), and metastatic disease. The size and maximum standardized uptake values (SUVmax) were measured for all lesions. All of the patients also underwent whole-body 131I-metaiodobenzylgunanidine (131I-MIBG) scintigraphy and conventional imaging (CT/MR imaging) of the head and neck region. Their results were compared with those of 68Ga-DOTANOC PET/CT. Results: 68Ga-DOTANOC PET/CT findings were positive in all 26 patients, and 78 lesions were detected. PET/CT imaging demonstrated 45 HNPS, 10 non-HNPs, and 23 metastatic sites. Fifteen patients (57.6%) had more than one site of disease on PET/CT. Among 45 HNPs, 26 were carotid body tumors (CBTs), 15 glomus jugulare, 3 glomus tympanicum, and 1 laryngeal paraganglioma. A positive correlation was seen between size and SUVmax of HNPs (ρ = 0.323; P = 0.030). The SUVmax of the CBTs was higher than that of jugulotympanic paragangliomas (P = 0.026). No correlation was seen between size and SUVmax (ρ = 0.069; P = 0.854) of non-HNPs. The size and SUVmax of non-HNPs were significantly less than those of HNPs (P = 0.029 and 0.047, respectively). 131I-MIBG scintigraphy showed only 30 of the 78 lesions and was inferior to PET/CT (P < 0.0001). Conventional imaging (CT/MR imaging) was positive for 42 of 49 head and neck lesions and was inferior to PET/CT on direct comparison (P = 0.015). A combination of CT/MR imaging and 131I-MIBG scintigraphy detected only 53 of 78 (67.9%) lesions and was also inferior to PET/CT (P < 0.0001). Conclusion: 68Ga-DOTANOC PET/CT is useful for the baseline evaluation of patients with HNPs and can demonstrate synchronous paragangliomas at other sites and distant metastases. It is superior to 131I-MIBG scintigraphy and conventional imaging (CT/MR imaging) for this purpose.

18F-FDG PET-CT in the diagnosis of tumor thrombus: can it be differentiated from benign thrombus?

ObjectiveThe correct diagnosis of tumor thrombosis and its differentiation from benign thrombus can change patient management and prevent unnecessary anticoagulation treatment. This study was aimed at evaluating the role of fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) in the diagnosis of tumor thrombosis, and its differentiation from benign thromboembolism. MethodsWe conducted a retrospective review of FDG PET-CT scans of patients who underwent the study for staging/restaging of a known malignancy and had FDG-avid thrombosis. Maximum standardized uptake value (SUVmax) of the thrombus, SUVmax of tumor (if any), and SUVmax of mediastinal blood pool were calculated. PET-CT results were confirmed with clinical follow-up, structural imaging, and histopathology when available. ResultsA total of 24 patients (15 male and nine female) with a mean age of 43.8 years (range: 3–72 years; median: 47.5 years) were evaluated. On the basis of structural imaging and clinical follow-up, 10 patients had benign and 14 patients had tumor thrombosis. On FDG PET-CT, uptake in the thrombus was linear in 18 patients and focal in six patients. The most common site of thrombosis was the inferior vena cava. The mean SUVmax was 3.2 (range: 2.3–4.6; median: 3.3) in the benign thrombosis group and was 6.0 (range: 2.3–13.8; median: 3.3) in the tumor thrombosis group. The difference in SUVmax was significant (P=0.013). On receiver operating characteristic analysis, a cut-off SUVmax of 3.63 (sensitivity: 71.4% and specificity: 90%) was obtained to differentiate tumor thrombus from benign thromboembolism. In six patients, FDG PET-CT detected occult vascular thrombosis. ConclusionFDG PET-CT can detect active tumor thrombosis and is helpful in differentiating it from benign thrombus.

⁶⁸Ga-DOTANOC PET/CT in patients with carcinoma of unknown primary of neuroendocrine origin.

Objective: To evaluate the role of 68Ga-DOTANOC (68Gallium-labeled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-NaI3-octreotide) PET/CT for localization of the primary tumor in patients with carcinoma of unknown primary of neuroendocrine origin. Material and Methods: Twenty patients (median age, 55 years; male 10) with histopathologically proven metastatic neuroendocrine tumor and no localization of primary tumor on conventional imaging were included in the study. PET/CT was done after injection of 132–222 MBq (4–6 mCi) of 68Ga-DOTANOC. Images were evaluated by 2 experienced nuclear medicine physicians both qualitatively as well as quantitatively (maximum standardized uptake value). Histopathology (when available) and/or follow-up imaging with biochemical markers were taken as reference standard. Results: 68Ga-DOTANOC PET/CT localized the primary tumor in 12/20 (60%) patients. Midgut was the most common site of primary tumor (n = 9); duodenum (4), ileum (4), and colon (1). In 1 patient each the primary was localized to the pancreas, stomach, and lung. In these 12 patients, significant correlation was found between maximum standardized uptake value of primary tumor and metastasis (&rgr; = 0.615; P = 0.041). Even in patients in whom no primary tumor was localized, additional sites of metastatic disease were observed when compared with conventional imaging, mostly in lymph nodes and bones. There was a change in management in 3/20 patients (15%), who underwent surgery. In the remaining 17 patients, demonstration of somatostatin receptor expression by PET/CT made them suitable candidate for peptide receptor radionuclide therapy. Conclusion: 68Ga-DOTANOC PET/CT seems to be a promising modality for detecting primary tumor in patients with carcinoma of unknown primary of neuroendocrine origin.

Dual tracer functional imaging of gastroenteropancreatic neuroendocrine tumors using 68Ga-DOTA-NOC PET-CT and 18F-FDG PET-CT: competitive or complimentary?

Objective This study aimed to compare the diagnostic performance of 68Ga-DOTANOC PET/CT with 18F-FDG PET/CT in the patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Patients and Methods Data of 51 patients with definite histological diagnosis of GEP-NET who underwent both 68Ga-DOTA-NOC PET-CT and 18F-FDG PET-CT within a span of 15 days were selected for this retrospective analysis. Sensitivity, specificity, and predictive values were calculated for 68Ga-DOTA-NOC PET-CT and 18F-FDG PET-CT, and results were compared both on patientwise and regionwise analysis. Results 68Ga-DOTA-NOC PET-CT is superior to 18F-FDG PET-CT on patientwise analysis (P < 0.0001). On regionwise analysis, 68Ga-DOTA-NOC PET-CT is superior to 18F-FDG PET-CT only for lymph node metastases (P < 0.003). Although 68Ga-DOTA-NOC PET-CT detected more liver and skeletal lesions compared with 18F-FDG PET-CT, the difference was not statistically significant. In addition, the results of combined imaging helped in selecting candidates who would undergo the appropriate mode of treatment, whether octreotide therapy or conventional chemotherapy Conclusions 68Ga-DOTA-NOC PET-CT seems to be superior to 18F-FDG PET-CT for imaging GEP-NETs. However, their role seems to be complementary because combination of 68Ga-DOTA-NOC PET-CT and 18F-FDG PET-CT in such patients helps demonstrate the total disease burden and segregate them to proper therapeutic groups.

Prospective evaluation of 68Ga-DOTA-NOC PET-CT in patients with recurrent medullary thyroid carcinoma: comparison with 18F-FDG PET-CT.

ObjectiveTo prospectively evaluate the role of 68Ga-labelled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-NaI3-octreotide (68Ga-DOTA-NOC) PET-CT in patients with recurrent medullary thyroid carcinoma (MTC) and compare the same with 18F-fluorodeoxyglucose (18F-FDG) PET-CT. Materials and methodsFifty-two consecutive patients with recurrent MTC based on raised serum calcitonin levels underwent 68Ga-DOTA-NOC PET-CT. In addition, 41 patients also underwent 18F-FDG PET-CT. PET-CT images were evaluated by two experienced nuclear medicine physicians both qualitatively and quantitatively (standardized uptake value). Histopathology (when available), correlation with conventional imaging modalities (ultrasonography/CT/MRI) and subsequent clinical/imaging follow-up were used as reference standard. Serum calcitonin levels were correlated with findings of PET-CT. ResultsOverall, 68Ga-DOTA-NOC PET-CT showed a sensitivity of 80.7% [95% confidence interval (CI) 67.4–90.3] and a positive predictive value of 100% (95% CI 91.5–100) for detecting recurrent MTC. When both were available (n=41), 68Ga-DOTA-NOC PET-CT proved superior to 18F-FDG PET-CT with a higher sensitivity (75.61 vs. 63.4%). However, the difference was statistically not significant (P=0.179). 68Ga-DOTA-NOC PET-CT was superior to 18F-FDG PET-CT for detecting recurrence in cervical lymph nodes (P<0.001). Both modalities were concordant in 75% of cases. No significant cut-off level of calcitonin could be derived for either 68Ga-DOTA-NOC or 18F-FDG PET-CT. ConclusionBoth 68Ga-DOTA-NOC PET-CT and 18F-FDG PET-CT are able to localize disease recurrence in patients with MTC, and their role appears to be complementary for this purpose.

Can hybrid SPECT-CT overcome the limitations associated with poor imaging properties of 131I-MIBG?: Comparison with planar scintigraphy and SPECT in pheochromocytoma.

Objective This study aimed to evaluate the incremental value of 131I-MIBG hybrid SPECT-CT over planar scintigraphy (PS) and SPECT alone in patients with clinical or biochemical suspicion of pheochromocytoma. Methods A total of 126 adrenals of 63 patients (mean [SD] age, 28.6 [15.7] years; male patients, n = 34; female patients, n = 29) with clinical or biochemical suspicion of pheochromocytoma were retrospectively evaluated. All patients had undergone 131I-MIBG SPECT-CT of adrenal region. The PS, SPECT, and SPECT-CT images were independently evaluated by 2 nuclear medicine physicians with 6 years (R1) and 2 years (R2) experience and in separate sessions 1 week apart. A scoring scale of 1 to 5 was used, in which 1 is definitely abnormal, 2 is probably abnormal, 3 is indeterminate, 4 is probably normal, and 5 is definitely normal. Sensitivity, specificity, predictive values were calculated taking a score 2 or less as abnormal. With receiver operating characteristic (ROC) curve analysis, areas under the curve (AUC) were calculated for each modality and compared. Histopathology and/or clinical/imaging follow-up were taken as reference standard. Results Of the 126 adrenals evaluated, 29 were indeterminate on PS for R1 and 48 for R2, 39 were indeterminate on SPECT for both, and on SPECT-CT, 1 was indeterminate for R1 and 2 for R2. SPECT-CT correctly characterized 28 of 29 indeterminate adrenals on PS and 37 of 39 indeterminate adrenals on SPECT for R1. Similarly, for R2, SPECT-CT correctly characterized 45 of 48 indeterminate adrenals on PS and 33 of 39 indeterminate adrenals on SPECT. On ROC comparison, PS was inferior to SPECT (P = 0.040 for R1; P < 0.001 for R2) and SPECT-CT (P = 0.001 for R1; P < 0.001 for R2) for both the observers. Moreover, SPECT was inferior to SPECT-CT for both the observers (P = 0.017 for R1 and P = 0.001 for R2). Accuracy of SPECT-CT (R1, 97.6%; R2, 97.6%) was higher than PS (R1, 91.2%; R2, 84.1%) and SPECT (R1, 94.4%; R2, 86.5%). Interobserver agreement was highest for SPECT-CT (&kgr; = 0.966) as compared with PS (&kgr; = 0.815) and SPECT (&kgr; = 0.826). Conclusions 131I-MIBG hybrid SPECT-CT shows high sensitivity and specificity for characterizing adrenal lesions in patients with clinical or biochemical suspicion of pheochromocytoma and is superior to PS and SPECT alone. It will be especially useful in countries where 123I-MIBG is not available.

Imaging thrombus in cancer patients with FDG PET–CT

The incidence of thrombosis in patients with underlying primary malignancy is high. The thrombus may be the more common venous thromboembolism (VTE) or the rare tumour thrombus. VTE is a common entity in cancer patients and is managed with anticoagulant therapy, while tumour thrombosis requires aggressive multimodality management. Conventional imaging modalities, including ultrasonography, venography, contrast-enhanced computed tomography, and magnetic resonance imaging, are used routinely in such cases. With its increasing use in oncology, more and more such thrombi are encountered on 18F-fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET–CT). Accurate characterisation of these lesions is of utmost importance owing to complementary functional information which it provides. FDG PET–CT has been found to be helpful in this context. This pictorial review discusses and illustrates the imaging features of thrombosis on FDG PET–CT.

Accuracy of 68Ga DOTANOC PET/CT Imaging in Patients With Multiple Endocrine Neoplasia Syndromes.

Objective The aim of this study was to evaluate the role of 68Ga DOTANOC PET/CT imaging in patients with multiple endocrine neoplasia (MEN) syndromes. Patients and Methods Data of 33 patients (age, 33.5 [13.8] years; male 14/female 19) with MEN syndromes (MEN 1, 9; MEN 2A, 19; MEN 2B, 5) who underwent 41 68Ga DOTANOC PET/CT studies were retrospectively analyzed. Twenty PET/CTs were done for staging and 21 for restating. PET/CT images were evaluated in consensus by 2 nuclear medicine physicians, qualitatively and semiquantitatively (SUVmax). A combination of histopathology, clinical, and biomarker follow-up was taken as reference standard. Results Of the total 41 68Ga DOTANOC PET/CTs, 34 were interpreted as positive for neuroendocrine tumors (NETs) and 7 as negative. The patientwise sensitivity of PET/CT was 94% (95% confidence interval [CI], 80–99), specificity was 71% (95% CI, 29–96), positive predictive value was 94% (95% CI, 80–99), negative predictive value was 71% (95% CI, 29–96), and accuracy was 90%. A total of 74 disease sites were demonstrated on PET/CT, including 41 primary NETs (pancreas, 10; stomach, 2; pheochromocytoma, 10; medullary thyroid carcinoma, 19), 31 metastatic sites (lymph node, 15; liver, 10; bone, 4; lung, 1; breast, 1), and 2 parathyroid adenomas. Lesionwise sensitivity, positive predictive value, and accuracy of PET/CT were 93%, 96%, and 90% overall, 89%, 95%, and 85% for primary tumors, and 100%, 97%, and 97% for metastasis, respectively. Among primary tumors, the SUVmax of medullary thyroid carcinoma was significantly lower than gastro pancreatic NETs (P = 0.003) and pheochromocytomas (P = 0.003). No site-specific difference was seen in SUVmax of metastatic lesions. Conclusions 68Ga DOTANOC PET/CT shows high diagnostic accuracy in MEN syndrome and can demonstrate both primary and metastatic NETs in these patients.