Diagnostic performance of Gallium-68 somatostatin receptor PET and PET/CT in patients with thoracic and gastroenteropancreatic neuroendocrine tumours: a meta-analysis

Neuroendocrine tumours: the role of imaging for diagnosis and therapy

In patients with neuroendocrine tumours (NETs), a combination of morphological imaging and nuclear medicine techniques is mandatory for primary tumour visualization, staging and evaluation of somatostatin receptor status. CT and MRI are well-suited for discerning small lesions that might escape detection by single photon emission tomography (SPECT) or PET, as well as for assessing the local invasiveness of the tumour or the response to therapy. Somatostatin receptor imaging, by (111)In-pentetreotide scintigraphy or PET with (68)Ga-labelled somatostatin analogues, frequently identifies additional lesions that are not visible on CT or MRI scans. Currently, somatostatin receptor scintigraphy with (111)In-pentetreotide is the more frequently available of the two techniques to determine somatostatin receptor expression and is needed to select patients for peptide receptor radionuclide therapy. In the future, because of its higher sensitivity, PET with (68)Ga-labelled somatostatin analogues is expected to replace somatostatin receptor scintigraphy. Whereas (18)F-FDG-PET is only used in high-grade neuroendocrine cancers, PET-CT with (18)F-dihydroxy-L-phenylalanine or (11)C-5-hydroxy-L-tryptophan is a useful problem-solving tool and could be considered for the evaluation of therapy response in the future. This article reviews the role of imaging for the diagnosis and management of intestinal and pancreatic NETs. Response evaluation and controversies in NET imaging will also be discussed.

Role of 68Ga-DOTATOC PET/CT in initial evaluation of patients with suspected bronchopulmonary carcinoid

PURPOSE

The objective of this study was to evaluate the role of (68)Ga-DOTATOC positron emission tomography (PET)/CT scan in patients with suspected pulmonary carcinoid tumour and to compare its results with (18)F-fluorodeoxyglucose (FDG) PET/CT scan.

METHODS

In this prospective study, 32 patients (age 34.22 ± 12.03 years; 53.1 % female) with clinical suspicion of bronchopulmonary carcinoid were evaluated with (68)Ga-DOTATOC PET/CT and (18)F-FDG PET/CT. The two imaging modalities were compared, considering the tissue diagnosis as the reference standard.

RESULTS

Based on the reference standard 26 cases were carcinoid tumours [21 typical carcinoids (TC) and 5 atypical carcinoids (AC)] and 6 cases were non-carcinoid tumours. The sensitivity, specificity and accuracy of (68)Ga-DOTATOC PET/CT in the diagnosis of pulmonary carcinoid tumour were 96.15, 100 and 96.87 % respectively, whereas those of (18)F-FDG PET/CT were 78.26, 11.1 and 59.37 % respectively. The maximum standardised uptake value (SUV max) of TC on (68)Ga-DOTATOC PET/CT scan ranged from 3.58 to 55, while that of AC ranged from 1.1 to 32.5. (18)F-FDG PET/CT was true-positive in all cases of AC and false-negative in eight cases of TC (sensitivity for TC 61.9 % and for AC 100 %).

CONCLUSION

(68)Ga-DOTATOC PET/CT is a useful imaging investigation for the evaluation of pulmonary carcinoids. (18)F-FDG PET/CT scan suffers from low sensitivity and specificity in differentiating the pulmonary carcinoids from other tumours.

A rare case of ectopic adrenocorticotropic hormone syndrome caused by a metastatic neuroendocrine tumor of the pancreas detected by 68Ga-DOTANOC and 18F-FDG PET/CT

We report a rare case of ectopic adrenocorticotropic hormone (ACTH) syndrome caused by a metastatic neuroendocrine tumor (NET) of the pancreas detected by PET/CT using different tracers. A 43-year-old female patient with Cushing syndrome (CS) by suspected ectopic ACTH secretion underwent a 68Ga-DOTANOC and a 18F-FDG PET/CT. Both these functional imaging techniques revealed increased tracer uptake in a pancreatic mass and multiple liver metastases. Histology showed the presence of a mildly differentiated pancreatic NET. 68Ga-DOTANOC PET/CT may be a useful functional imaging method, complementary to 18F-FDG PET/CT, in detecting ACTH-secreting pancreatic NETs.

Combination of cross-sectional and molecular imaging studies in the localization of gastroenteropancreatic neuroendocrine tumors

Molecular imaging modalities exploit aspects of neuroendocrine tumors (NET) pathophysiology for both diagnostic imaging and therapeutic purposes. The characteristic metabolic pathways of NET determine which tracers are useful for their visualization. In this review, we summarize the diagnostic value of all available molecular imaging studies, present data about their use in daily practice in NET centers globally, and finally make recommendations about the appropriate use of those modalities in specific clinical scenarios. Somatostatin receptor scintigraphy (SRS) continues to have a central role in the diagnostic workup of patients with NET, as it is also widely available. However, and despite the lack of prospective randomized studies, many NET experts predict that Gallium-68 ((68)Ga)-DOTA positron emission tomography (PET) techniques may replace SRS in the future, not only because of their technical advantages, but also because they are superior in patients with small-volume disease, in patients with skeletal metastases, and in those with occult primary tumors. Carbon-11 ((11)C)-5-hydroxy-L-tryptophan (5-HTP) PET and (18)F-dihydroxyphenylalanine ((18)F-DOPA) PET are new molecular imaging techniques of limited availability, and based on retrospective data, their sensitivities seem to be inferior to that of (68)Ga-DOTA PET. Glucagon-like-peptide-1 (GLP-1) receptor imaging seems promising for localization of the primary in benign insulinomas, but is currently available only in a few centers. Fluorine-18 ((18)F)-fluorodeoxyglucose ((18)F-FDG) PET was initially thought to be of limited value in NET, due to their usually slow-growing nature. However, according to subsequent data, (18)F-FDG PET is particularly helpful for visualizing the more aggressive NET, such as poorly differentiated neuroendocrine carcinomas, and well-differentiated tumors with Ki67 values >10%. According to limited data, (18)F-FDG-avid tumor lesions, even in slow-growing NET, may indicate a more aggressive disease course. When a secondary malignancy has already been established or is strongly suspected, combining molecular imaging techniques (e.g. (18)F-FDG PET and (68)Ga-DOTA PET) takes advantage of the diverse avidities of different tumor types to differentiate lesions of different origins. All the above-mentioned molecular imaging studies should always be reviewed and interpreted in a multidisciplinary (tumor board) meeting in combination with the conventional cross-sectional imaging, as the latter remains the imaging of choice for the evaluation of treatment response and disease follow-up.

The role of combined Ga-DOTANOC and (18)FDG PET/CT in the management of patients with pancreatic neuroendocrine tumors

PURPOSE

The aim of this study was to evaluate the effect of combined (68)Ga and (18)F-FDG PET/CT on treatment management for patients with pancreatic neuroendocrine tumor (PNET).

METHODS

Between January 2012 and April 2014, 49 consecutive patients with a cytologically and/or histologically proven diagnosis of PNET underwent combined (68)Ga and (18)FDG PET/CT on the same day.

RESULTS

The study group consisted of 21 males and 28 females with a median age of 59 years. Disease detection was achieved in 48 out of the 49 cases with (68)Ga imaging, and in 36 of the 49 cases with (18)FDG PET/CT. These results corresponded to sensitivities of 98% for (68)Ga versus 73% for (18)FDG PET/CT. Patients with NET-G1/NET-G2 had a positive (68)Ga and negative (18)FDG PET/CT in 13 cases, whereas both (68)Ga and (18)FDG PET/CT were positive in 27 cases. Patients with NEC-G3 were positive by both (68)Ga and (18)FDG PET/CT in 7 cases and positive only by (18)FDG in 1 case. Another NEC-G3 patient was only positive by (68)Ga PET/CT. The median Ki67 was 7% for (68)Ga PET/CT-positive tumors and 10% for tumors with both (68)Ga and (18)FDG PET/CT positivity (p = 0.130). Half of the patients with a prevalent uptake of (18)FDG (n = 7) had an NEC-G3 compared with 12% of patients with a prevalent uptake of (68)Ga (p = 0.012). There were no significant differences between patients with positive (68)Ga and those with positive (18)FDG with regards to treatment choice.

CONCLUSIONS

The association of (18)FDG slightly increases sensitivity of (68)Ga PET/CT alone in the diagnosis of PNET. A combined dual tracer PET/CT does not influence the choice of treatment strategy.

Predictive value of 68Ga-DOTANOC PET/CT in patients with suspicion of neuroendocrine tumors: is its routine use justified?

OBJECTIVE

The objective of this study was to evaluate the predictive value of Ga-DOTANOC PET/CT in patients with suspected neuroendocrine tumor (NET).

METHODS

Data of 164 patients (mean age, 42.5 ± 17.3 years; 54.8% male) who underwent Ga-DOTANOC PET/CT for suspected NET were retrospectively analyzed. Neuroendocrine tumor was suspected based on clinical features (n = 94) and/or raised biochemical markers (n = 83, serum chromogranin A, gastrin, serum/urinary catecholamines, insulin/C-peptide, and 5-hydroxytrytophan/5-hydroxyindoleacetic acid) and/or imaging findings (n = 93). PET/CT images were reviewed by 2 experienced nuclear medicine physicians, and any nonphysiological Ga-DOTANOC uptake was taken as positive for NET. Histopathology (n = 55) and clinical/imaging follow-up (n = 109; median, 11 months) was used as reference standard.

RESULTS

Based on the reference standard, 97 of 164 patients had NET. Ga-DOTANOC PET/CT was positive for NET in 101 and negative in 63 patients. Primary tumor was demonstrated in 90 patients (commonest site-pancreas) and metastasis in 30 (commonest site-liver). PET/CT was true positive in 92 patients, true negative in 58, false positive in 9, and false negative in 5. The overall sensitivity was 94.8%, specificity was 86.5%, positive predictive value was 91%, negative predictive value was 92%, and accuracy was 91.4%. The accuracy of PET-CT in patients with clinical features of NET was 90.4%, with raised biochemical markers was 86.7%, and with imaging findings suggestive of NET was 93.5%. No difference was seen in the accuracy in patients with or without clinical symptoms (P = 0.794), raised versus those with normal/unknown biochemical markers (P = 0.094), and suggestive imaging versus those with negative/unavailable imaging (P = 0.420).

CONCLUSIONS

Ga-DOTANOC PET-CT shows high positive and negative predictive values in patients with suspected NET and can be routinely used for this purpose.

PET/CT imaging of neuroendocrine tumors with (68)Gallium-labeled somatostatin analogues: An overview and single institutional experience from India

Neuroendocrine tumors (NETs) are rare neoplasms characterized by overexpression of somatostatin receptors (SSTRs). Functional imaging plays a crucial role in management of NETs. Recently, positron emission tomography/computed tomography (PET/CT) with (68)Gallium ((68)Ga)-labeled somatostatin analogues has shown excellent results for imaging of NETs and better results than conventional SSTR scintigraphy. In this review we have discussed the utility of (68)Ga-labeled somatostatin analogue PET/CT in NETs for various established and potential indications. In addition we have also shared our own experience from a tertiary care center in India.

Quantitative and qualitative intrapatient comparison of 68Ga-DOTATOC and 68Ga-DOTATATE: net uptake rate for accurate quantification

Quantitative imaging and dosimetry are crucial for individualized treatment during peptide receptor radionuclide therapy (PRRT). (177)Lu-DOTATATE and (68)Ga-DOTATOC/(68)Ga-DOTATATE are used, respectively, for PRRT and PET examinations targeting somatostatin receptors (SSTRs) in patients affected by neuroendocrine tumors. The aim of the study was to quantitatively and qualitatively compare the performance of (68)Ga-DOTATOC and (68)Ga-DOTATATE in the context of subsequent PRRT with (177)Lu-DOTATATE under standardized conditions in the same patient as well as to investigate the sufficiency of standardized uptake value (SUV) for estimation of SSTR expression.

METHODS

Ten patients with metastatic neuroendocrine tumors underwent one 45-min dynamic and 3 whole-body PET/CT examinations at 1, 2, and 3 h after injection with both tracers. The number of detected lesions, SUVs in lesions and normal tissue, total functional tumor volume, and SSTR volume (functional tumor volume multiplied by mean SUV) were investigated for each time point. Net uptake rate (Ki) was calculated according to the Patlak method for 3 tumors per patient.

RESULTS

There were no significant differences in lesion count, lesion SUV, Ki, functional tumor volume, or SSTR volume between (68)Ga-DOTATOC and (68)Ga-DOTATATE at any time point. The detection rate was similar, although with differences for single lesions in occasional patients. For healthy organs, marginally higher uptake of (68)Ga-DOTATATE was observed in kidneys, bone marrow, and liver at 1 h. (68)Ga-DOTATOC uptake was higher in mediastinal blood pool at the 1-h time point (P = 0.018). The tumor-to-liver ratio was marginally higher for (68)Ga-DOTATOC at the 3-h time point (P = 0.037). Blood clearance was fast and similar for both tracers. SUV did not correlate with Ki linearly and achieved saturation for a Ki of greater than 0.2 mL/cm(3)/min, corresponding to an SUV of more than 25.

CONCLUSION

(68)Ga-DOTATOC and (68)Ga-DOTATATE are suited equally well for staging and patient selection for PRRT with (177)Lu-DOTATATE. However, the slight difference in the healthy organ distribution and excretion may render (68)Ga-DOTATATE preferable. SUV did not correlate linearly with Ki and thus may not reflect the SSTR density accurately at its higher values, whereas Ki might be the outcome measure of choice for quantification of SSTR density and assessment of treatment outcome.

Prospective of ⁶⁸Ga-radiopharmaceutical development

Positron Emission Tomography (PET) experienced accelerated development and has become an established method for medical research and clinical routine diagnostics on patient individualized basis. Development and availability of new radiopharmaceuticals specific for particular diseases is one of the driving forces of the expansion of clinical PET. The future development of the ⁶⁸Ga-radiopharmaceuticals must be put in the context of several aspects such as role of PET in nuclear medicine, unmet medical needs, identification of new biomarkers, targets and corresponding ligands, production and availability of ⁶⁸Ga, automation of the radiopharmaceutical production, progress of positron emission tomography technologies and image analysis methodologies for improved quantitation accuracy, PET radiopharmaceutical regulations as well as advances in radiopharmaceutical chemistry. The review presents the prospects of the ⁶⁸Ga-based radiopharmaceutical development on the basis of the current status of these aspects as well as wide range and variety of imaging agents.

Diagnostic performance of fluorine-18-fluorodeoxyglucose positron emission tomography in patients with Merkel cell carcinoma: a systematic review and meta-analysis

BACKGROUND

Some studies reported the usefulness of fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and PET/computed tomography (CT) in patients with Merkel cell carcinoma (MCC).

OBJECTIVE

The aim of this study was to systematically review and meta-analyze published data about the diagnostic performance of 18F-FDG PET and PET/CT in patients with MCC.

METHODS

A comprehensive literature search of studies published through June 2013 regarding 18F-FDG PET and PET/CT in patients with MCC was performed. All retrieved studies were reviewed and qualitatively analyzed. Pooled sensitivity, specificity, positive and negative likelihood ratio (LR+ and LR−) and diagnostic odds ratio (DOR) of 18F-FDG PET or PET/CT in patients with MCC on a per examination-based analysis were calculated. The area under the summary receiver operating characteristic (ROC) curve was calculated to measure the accuracy of 18F-FDG PET or PET/CT in these patients.

RESULTS

Ten studies comprising 329 patients (549 scans) with MCC were included in the qualitative analysis (systematic review) and discussed. The quantitative analysis (meta-analysis) of six selected studies (including 92 patients with MCC) provided the following results on a per examination-based analysis: sensitivity was 90 % (95 % CI 80–96), specificity 98 % (95 % CI 90–100), LR+ 12 (95 % CI 4.3–33.0), LR− 0.15 (95 % CI 0.08–0.28), and DOR 86.8 (95 % CI 23–327). The area under the summary ROC curve was 0.96. No significant statistical heterogeneity between the studies was found.

CONCLUSIONS

In patients with MCC, 18F-FDG PET or PET/CT demonstrated high sensitivity and specificity, being accurate methods in this setting. Nevertheless, the literature focusing on the use of PET and PET/CT in MCC still remains limited. Prospective studies are needed to substantiate the high diagnostic accuracy of these methods in MCC.

Metachronous appearance of second malignancies in medullary thyroid carcinoma (MTC) patients: a diagnostic challenge and brief review of the literature

Medullary thyroid carcinoma (MTC) is a rare tumour which frequently occurs in the context of the multiple endocrine neoplasia syndromes, where it coexists with other usually benign tumours. The clinical picture varies and distant metastases are frequently present at diagnosis. Calcitonin levels are elevated in the presence of metastatic disease. Two MTC cases are presented, which had elevated postoperative calcitonin levels. Imaging revealed lung lesions which were originally attributed to metastatic disease from the MTC. However, at follow-up, these cases presented unusual features. The rapid increase in the lung lesions and the development of hypercalcaemia in the first patient suggested a second unrelated tumour. Biopsy of the lung lesion was compatible with lung adenocarcinoma. In the second patient, the appearance of a liver mass, although calcitonin levels remained stable, led to biopsy of the lesion: this was negative for calcitonin and compatible with metastatic lung adenocarcinoma. These MTC cases show that further malignancies may coexist with MTC and may obscure the clinical picture and influence the therapeutic decisions, especially in the case of metastatic disease. Features such as unusual imaging characteristics and the development of hypercalcemia, never encountered in MTC outside the MEN2 syndromes, as well as 'disproportionately' low calcitonin levels, incompatible with extensive metastatic disease, were the factors that led to further work-up. Both the cases subsequently proved to carry an unsuspected second malignancy. It is crucial to discriminate the metastatic lesion attributed to MTC from another coexisting primary malignancy, because different therapeutic strategies are needed for each setting.

Somatostatin receptor-based PET/CT of intracranial tumors: a potential area of application for 68 Ga-DOTA peptides?

OBJECTIVE

Similar to neuroendocrine tumors (NETs) at other sites, a wide array of intracranial tumors also express somatostatin receptors (SSTRs). This expression can be exploited for both imaging and therapy. The introduction of (68)Ga-labeled tetraazacyclododecanetetraacetic acid (DOTA)-peptide PET/CT has given new dimension to SSTR-based imaging because of its improved sensitivity and excellent spatial resolution.

CONCLUSION

However, in contrast to gastropancreatic and bronchopulmonary NETs, limited literature is available regarding the use of (68)Ga-DOTA-peptide PET/CT in intracranial tumors. Here, we briefly review the available literature and highlight the potential role that (68)Ga-DOTA-peptide PET/CT can play in the management of intracranial tumors.

Imaging features of pancreatic tumors in children: 13-year experience at a pediatric tertiary hospital

BACKGROUND

Pancreatic tumors are rare in children, resulting in limited information regarding their frequency and imaging appearances.

OBJECTIVE

To review all pancreatic tumors seen in children over a decade at a large tertiary pediatric institution and to describe multimodality imaging findings.

MATERIALS AND METHODS

We conducted a retrospective review of imaging studies performed in children with pancreatic tumors between January 2000 and December 2012, analyzing imaging features on available US, CT and MR examinations. We reviewed patient charts for clinical features, management and final diagnosis.

RESULTS

We included 23 children in this study. Of these, 12 had solid and papillary epithelial neoplasms (SPEN), 3 had neuroendocrine tumors, 3 had lymphoma, and 1 each had hemangioendothelioma, benign congenital cysts with adipose tissue, dendritic cell sarcoma, metastatic rhabdomyosarcoma, and lipoma. All children with SPEN were teenage girls. SPEN showed characteristic imaging features including well-defined margins with surrounding capsule, solid-cystic components and hemorrhage.

CONCLUSION

Pancreatic tumors are uncommon in children. SPEN is the most common tumor and is seen predominantly in teenage girls and shows characteristic imaging features.

Initial impact of a systematic multidisciplinary approach on the management of patients with gastroenteropancreatic neuroendocrine tumor

According to the international guidelines, a multidisciplinary approach is currently advised for the optimal care of patients with a gastroenteropancreatic neuroendocrine tumor (GEP NET). In our institution (tertiary care center), a systematic multidisciplinary approach was established in May 2007. In this study, we have aimed to assess the initial impact of establishing a systematic multidisciplinary approach to the management of GEP NET patients. We have collected and compared the biochemical, imaging, and pathological data and the therapeutic strategies in GEP NET patients diagnosed, treated, or followed-up from January 1993 to April 2007 versus GEP NET patients attending our institution after the multidisciplinary approach starting, from May 2007 to October 2008. Data of 91 patients before and 42 patients after the establishment of the multidisciplinary approach (total: 133 consecutive GEP NET patients) have been finally collected and analyzed. Before the establishment of the multidisciplinary approach, a lack of consistency in the biochemical, imaging, and pathological findings before treatment initiation as well as during follow-up of GEP NET patients was identified. These inconsistencies have been reduced by the systematic multidisciplinary approach. In addition, the therapeutic management of GEP NET patients has been altered by the multidisciplinary approach and became more consistent with recommended guidelines. We think that a systematic multidisciplinary approach significantly impacts on GEP NET patient care and should be established in all centers dealing with these tumors.

Somatostatin receptor-based molecular imaging and therapy for neuroendocrine tumors

Neuroendocrine tumors (NETs) are tumors originated from neuroendocrine cells in the body. The localization and the detection of the extent of NETs are important for diagnosis and treatment, which should be individualized according to the tumor type, burden, and symptoms. Molecular imaging of NETs with high sensitivity and specificity is achieved by nuclear medicine method using single photon-emitting and positron-emitting radiopharmaceuticals. Somatostatin receptor imaging (SRI) using SPECT or PET as a whole-body imaging technique has become a crucial part of the management of NETs. The radiotherapy with somatostatin analogues labeled with therapeutic beta emitters, such as lutetium-177 or yttrium-90, has been proved to be an option of therapy for patients with unresectable and metastasized NETs. Molecular imaging can deliver an important message to improve the outcome for patients with NETs by earlier diagnosis, better choice of the therapeutic method, and evaluation of the therapeutic response.

Pulmonary neuroendocrine tumor incidentally detected by (18)F-CH PET/CT

We report the case of a pulmonary neuroendocrine tumor (NET) incidentally detected by F-CH PET/CT performed during restaging in a 68-year-old patient affected by prostate cancer. To clarify the nature of the pulmonary lesion, the patient underwent a CT-guided biopsy which revealed the presence of a pulmonary NET. A subsequent Ga-DOTANOC PET/CT demonstrated the somatostatin receptor expression in the pulmonary lesion. The patient underwent a right lung lobectomy; at pathology, a well-differentiated NET was confirmed. Our case highlights that pulmonary NETs should be considered in the differential diagnosis of pulmonary lesions showing uptake of radiolabeled choline.

Somatostatin receptor PET/CT in neuroendocrine tumours: update on systematic review and meta-analysis

PURPOSE

Neuroendocrine tumours (NET) are uncommon and may be localized in many different places in the body. Traditional imaging has mainly been performed with CT and somatostatin receptor scintigraphy (SRS). Recently, it has become possible to use somatostatin receptor PET/CT (SMSR PET) instead, which might improve diagnostic quality. To evaluate the diagnostic quality of SMSR PET we performed a meta-analysis as an update of a previous study published in 2012.

METHODS

A literature search was performed searching MEDLINE, Embase and five other databases with a combination of the expressions "PET", "positron emission tomography", "neuroendocrine" and "NET". The search was updated to 31 December 2012. Studies were selected which evaluated the sensitivity and specificity of SMSR PET for NET in the thorax or abdomen with a study size of at least eight patients. The methodological quality of the included studies was evaluated with QUADAS-2.

RESULTS

Eight studies fulfilled the inclusion criteria and were selected for final analysis, and 14 articles from a previous meta-analysis were added for a total of 22 articles. A total of 2,105 patients were included in the studies, an increase from 567 in the previous meta-analysis. The pooled sensitivity was 93 % (95 % CI 91 - 94 %) and specificity 96 % (95 % CI 95 - 98 %). The area under the summary ROC curve was 0.98 (95 % CI 0.95 - 1.0). In the previous meta-analysis the pooled sensitivity was 93 % (95 % CI 91 - 95 %) and specificity 91 % (95 % CI 82 - 97 %).

CONCLUSION

SMSR PET has good diagnostic performance for evaluation of NET in the thorax and abdomen, better than SRS which has been the previous standard method. This meta-analysis gives further support for switching to SMSR PET.

Ectopic acromegaly due to growth hormone releasing hormone

Acromegaly secondary to extra-pituitary tumors secreting growth hormone releasing hormone (GHRH) is rarely encountered. We review the literature on ectopic acromegaly and present the index report of ectopic acromegaly secondary to GHRH secretion from a mediastinal paraganglioma. Clinical and pathological manifestations and therapeutic management of 99 patients with ectopic acromegaly are reviewed. Acromegaly secondary to ectopic GHRH secretion is usually caused by a neuroendocrine tumor in the lung and pancreas. We report an additional cause of ectopic acromegaly from a mediastinal paraganglioma. Diagnostic criteria of ectopic GHRH syndrome include biochemical and pathologic tumoral confirmation of GHRH secretion and expression. Management of ectopic acromegaly consists of surgical resection of the primary tumor and biochemical normalization, with possible adjuvant use of somatostatin analogs. The review demonstrates that there are several tumor types, including paragangliomas which may secrete GHRH, leading to acromegaly. Clinical and laboratory manifestations of the syndrome and challenges in diagnosis and management of these rarely encountered patients require early diagnosis and appropriate treatment to prevent long-term morbidity and mortality with ectopic acromegaly.

Recurrent acute-onset Cushing's syndrome 6 years after removal of a thymic neuroendocrine carcinoma: from ectopic ACTH to CRH

We describe a rare case of ectopic Cushing's syndrome that recurred 6 years after resection of a thymic neuroendocrine carcinoma. We discuss reasons for the differing clinical presentations, management, hormone profiles, as well as immunopathology. A 41-year-old male developed acute-onset Cushing's syndrome. Clinical presentation and laboratory results were compatible with ectopic adrenocorticotropin hormone (ACTH) production. Computerized tomography (CT) showed a 3.6 cm thymic tumor which was successfully resected. Plasma ACTH (P-ACTH) normalized the first postoperative day. Histopathology demonstrated a well-differentiated neuroendocrine carcinoma with diffuse positivity for ACTH and focal corticotropin-releasing hormone (CRH) reactivity in a few scattered cells. The patient was in remission for 6 years. He then again presented with acute-onset Cushing's syndrome. Fluorine-labeled dihydroxyphenylalanine ((18)F-DOPA) PET/CT showed local uptake in the mediastinum and he underwent repeat resection. However, P-ACTH remained increased (613 ng/l) and 24-h urinary cortisol was 36,720 nmol, suggesting incomplete tumor removal or metastatic spread. Metyrapone treatment was initiated but then withdrawn because the patient spontaneously recovered and cortisol metabolism gradually normalized within 3 weeks. Histopathology demonstrated a recurrent neuroendocrine carcinoma with the same features as the previous lesion but this time CRH was strongly positive in more numerous cells. Normalization of P-ACTH after primary surgery was compatible with ectopic ACTH production. However, the delayed fall in P-ACTH and serum cortisol is compatible with ectopic CRH production and stimulation of pituitary ACTH secretion, which gradually resolved. Although ectopic CRH production is very rare, the unusual dynamics illustrated here should raise the possibility of CRH production by a neuroendocrine tumor.

Diagnostic performance of positron emission tomography using ¹¹C-methionine in patients with suspected parathyroid adenoma: a meta-analysis

The diagnostic performance of positron emission tomography using ¹¹C-methionine (MET-PET) in detecting parathyroid adenoma has been investigated by several studies with conflicting results. Aim of our study is to meta-analyze published data about this topic. A comprehensive computer literature search of studies published in PubMed/MEDLINE, Scopus and Embase databases through May 2012 and regarding the diagnostic performance of MET-PET in patients with parathyroid adenoma was carried out. No language restriction was used. Only articles in which at least five patients with parathyroid adenoma underwent MET-PET were included in the meta-analysis. Pooled sensitivity and detection rate (DR) on a per patient-based analysis were calculated to assess the diagnostic performance of MET-PET. Nine studies comprising 258 patients with suspected parathyroid adenoma were included in this meta-analysis. Pooled sensitivity and DR values of MET-PET in patients with suspected parathyroid adenoma were 81 % (95 % confidence interval [95 %CI] 74-86 %) and 70 % (95 %CI 62-77 %), respectively, on a per patient-based analysis. The included studies were heterogeneous in their estimate of sensitivity and DR. Our meta-analysis demonstrates that MET-PET is a sensitive and reliable tool in patients with suspected parathyroid adenoma. Thus, this imaging method could be helpful in patients with diagnosis of primary hyperparathyroidism when conventional imaging techniques are negative or inconclusive in localizing parathyroid adenoma.

Detection rate of recurrent medullary thyroid carcinoma using fluorine-18 fluorodeoxyglucose positron emission tomography: a meta-analysis

Several studies evaluated the diagnostic performance of fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET), and positron emission tomography/computed tomography (PET/CT) in detecting recurrent medullary thyroid carcinoma (MTC) with conflicting results. Aim of our study is to meta-analyze published data about this topic. A comprehensive computer literature search of studies published in PubMed/MEDLINE, Scopus, and Embase databases through December 2011 and regarding FDG PET or PET/CT in patients with suspected recurrent MTC was carried out. Pooled detection rate (DR) on a per patient-based analysis was calculated to measure the diagnostic performance of FDG PET and PET/CT in this setting. A sub-analysis considering PET device used, serum calcitonin, carcino-embryonic antigen (CEA), calcitonin doubling time (CTDT), and CEA doubling time (CEADT) values was also performed. Twenty-four studies comprising 538 patients with suspected recurrent MTC were included. DR of FDG PET or PET/CT in suspected recurrent MTC on a per patient-based analysis was 59 % (95 % confidence interval: 54-63 %). Heterogeneity between the studies was revealed. DR increased in patients with serum calcitonin ≥ 1,000 ng/L (75 %), CEA ≥ 5 ng/ml (69 %), CTDT <12 months (76 %), and CEADT <24 months (91 %). In patients with suspected recurrent MTC FDG PET and PET/CT are associated with a non-optimal DR since about 40 % of suspected recurrent MTC remain usually unidentified. However, FDG PET and PET/CT could modify the patient management in a certain number of recurrent MTC because these methods are often performed after negative conventional imaging studies. DR of FDG PET and PET/CT increases in patients with higher calcitonin and CEA values and lower CTDT and CEADT values, suggesting that these imaging methods could be very helpful in patients with more aggressive disease.

Detection rate of recurrent medullary thyroid carcinoma using fluorine-18 dihydroxyphenylalanine positron emission tomography: a meta-analysis

RATIONALE AND OBJECTIVES

The aim of this study was to perform a meta-analysis of published data about the diagnostic performance of (18)F-dihydroxyphenylalanine (DOPA) positron emission tomography (PET) or PET/computed tomography (CT) in detecting recurrent medullary thyroid carcinoma (MTC).

MATERIALS AND METHODS

A comprehensive literature search of studies indexed in the PubMed/MEDLINE, Scopus, and Embase databases through January 2012 and regarding (18)F-DOPA PET or PET/CT in patients with suspected recurrent MTC was carried out. Pooled detection rates (DR) in per patient and per lesion analyses were calculated. A subanalysis considering serum levels of calcitonin and carcinoembryonic antigen, device used, and carbidopa pretreatment was also performed.

RESULTS

Eight studies including 146 patients with suspected recurrent MTC were included. The DRs of (18)F-DOPA PET and PET/CT in per patient and per lesion analyses were 66% and 71%, respectively. DRs significantly increased in patients with serum calcitonin ≥1000 ng/L (86%) and calcitonin doubling times <24 months (86%).

CONCLUSIONS

Fluorine-18-DOPA PET and PET/CT may be useful functional imaging methods in detecting recurrent MTC. The DR of recurrent MTC using these imaging methods increases in patients with higher calcitonin levels and lower calcitonin doubling times.

PET Imaging in Recurrent Medullary Thyroid Carcinoma

Purpose. To perform an overview about the role of positron emission tomography (PET) or PET/computed tomography (PET/CT) using different radiopharmaceuticals in recurrent medullary thyroid carcinoma (MTC) based on biochemical findings (increased tumor marker levels after primary surgery). Methods. A comprehensive literature search of studies published in PubMed/MEDLINE, Scopus, and Embase databases through February 2012 regarding PET or PET/CT in patients with recurrent MTC was performed. Results. Twenty-nine studies comprising 714 patients with suspected recurrent MTC were retrieved. Twenty-seven articles evaluated the role of fluorine-18-fluorodeoxyglucose (FDG) PET or PET/CT in recurrent MTC with conflicting results. Diagnostic accuracy of FDG-PET and PET/CT increased in MTC patients with higher calcitonin and carcinoembryonic antigen values, suggesting that these imaging methods could be very useful in patients with more advanced and aggressive disease. Eight articles evaluated the role of fluorine-18-dihydroxyphenylalanine (FDOPA) PET or PET/CT in recurrent MTC reporting promising results. Overall, FDOPA seems to be superior but complementary compared to FDG in detecting recurrent MTC. Few studies evaluating other PET tracers are also discussed. Conclusions. PET radiopharmaceuticals reflect different metabolic pathways in MTC. FDOPA seems to be the most useful PET tracer in detecting recurrent MTC based on rising levels of tumor markers. FDG may complement FDOPA in patients with more aggressive MTC.