Nuclear medicine imaging of gastro-entero-pancreatic neuroendocrine tumors. The key role of cellular differentiation and tumor grade: from theory to clinical practice

Nuclear medicine imaging for bone metastases assessment: what else besides bone scintigraphy in the era of personalized medicine?

Accurate detection and reliable assessment of therapeutic responses in bone metastases are imperative for guiding treatment decisions, preserving quality of life, and ultimately enhancing overall survival. Nuclear imaging has historically played a pivotal role in this realm, offering a diverse range of radiotracers and imaging modalities. While the conventional bone scan using 99mTc marked bisphosphonates has remained widely utilized, its diagnostic performance is hindered by certain limitations. Positron emission tomography, particularly when coupled with computed tomography, provides improved spatial resolution and diagnostic performance with various pathology-specific radiotracers. This review aims to evaluate the performance of different nuclear imaging modalities in clinical practice for detecting and monitoring the therapeutic responses in bone metastases of diverse origins, addressing their limitations and implications for image interpretation.

Pancreatic Neuroendocrine Tumor (Pan-NET) Presented by Abdominal Pain: A Case Report and Literature Review

A pancreatic neuroendocrine tumor (Pan-NET) is a rare neoplasm originating in the neuroendocrine system. Carcinoid syndrome occurs in approximately 19% of patients with functional Pan-NETs, typically when liver metastases occur. In this paper, we describe the case of a patient with a low-grade non-functional Pan-NET, but with a typical clinical presentation of carcinoid syndrome. An 81-year-old male was admitted to our Department of Internal Medicine at Cannizzaro Hospital (Catania, Italy) because of the onset of abdominal pain with nausea, loose stools, and episodic flushing. Firstly, an abdominal contrast-enhanced CT scan showed a small pancreatic hyper-vascular mass; then, a gallium-68 DOTATOC integrated PET/CT revealed an elevated expression of SSTR receptors. Serum chromogranin A and urinary 5-HIAA measurements were negative. We performed an endoscopic ultrasonography (EUS) by a fine-needle biopsy (EUS-FNB), allowing the immunostaining of a small mass (0.8 cm) and the diagnosis of a low-grade (G1) non-functional Pan-NET (NF-Pan-NET). Surgery was waived, while a follow-up strategy was chosen. The early recognition of Pan-NETs, although rare, is necessary to improve the patient's survival. Although helpful to allow for immunostaining, EUS-FNB needs to be warranted in future studies comparing EUS-FNB to EUS-FNA (fine-needle aspiration), which is, to date, reported as the tool of choice to diagnose Pan-NETs.

Effects of somatostatin analogs on uptake of radiolabeled somatostatin analogs on imaging: a systematic review and meta-analysis

Background

The imaging of somatostatin receptors (SSTRs) plays a significant role in imaging neuroendocrine tumors (NETs). However, there has been no clear definition on whether it is necessary to withdraw somatostatin analogs (SSAs) before SSTRs imaging. We aimed to assess whether nonradioactive SSAs affect the uptake of radiolabeled SSAs on imaging for NETs patients.

Methods

The databases of PubMed, Embase, and Web of Science (WoS) were searched until March 12, 2022 to identify eligible studies. Maximum standardized uptake values (SUVmax) in tumor and normal tissues were extracted, pooled, and compared before and after SSAs treatment. The change of tumor-to-background/liver ratio was also described. The quality of each study was assessed using the revised Quality Assessment of Diagnostic Accuracy Studies-2 tool.

Results

A total of 9 articles involving 285 patients were included and 5 studies using Gallium-68-labeled [1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid]-D-Phe1-Tyr3-Thr8-octreotide (68Ga-DOTATATE) were used for pooled evaluation. We found a significantly decreased SUVmax in the liver (9.56±2.47 vs. 7.62±2.12, P=0.001) and spleen (25.74±7.14 vs. 20.39±6.07, P=0.006) after SSAs treatment whereas no significant differences were observed in the uptake of thyroid, adrenal, and pituitary gland. For either primary tumor sites or metastases, the SUVmax did not change significantly before and after SSAs treatment. The tumor-to-liver/background ratio increased following SSAs therapy. High heterogeneity was observed across the studies, mainly due to inherent diversity of study design, sample size, and scanning technique.

Conclusions

Based on current evidence, long-acting SSAs therapy before imaging has no effect on the uptake of radiolabeled SSAs at tumor primary sites and metastatic lesions, but results in a significant reduction of uptake in the liver and spleen. These findings may implicate the unnecessary discontinuation of SSAs before radiolabeled SSAs imaging.

The New Radiolabeled Peptide 99mTcEDDA/HYNIC-TOC: Is It a Feasible Choice for Diagnosing Gastroenteropancreatic NETs?

(1) Background: The aim of our study is to reveal the advantages and limitations of the use of 99mTcEDDA/HYNIC-TOC (Tektrotyd®, Polatom) in the diagnosis of gastroenteropancreatic neuroendocrine tumors and to compare our results with the values obtained for 111In-pentetreotide and 68Ga-DOTA-peptides, routinely used in medical practice. (2) Methods: This retrospective monocentric study included 173 patients with gastroenteropancreatic neuroendocrine tumors who underwent 99mTcEDDA/HYNIC-TOC scans as part of their clinical management. The examination protocol included a whole-body scan acquired 2 h after the radiotracer's administration, with the SPECT/CT performed 4 h post-injection. Physiological and abnormal uptake were established by two experienced physicians and, based on the obtained results, sensitivity, specificity, accuracy, positive predictive value and negative predictive value were calculated. (3) Results: Our method presented a sensitivity of 90.5%, a specificity of 71.9%, and an accuracy of 84.3%, with a positive predictive value of 86.7% and a negative predictive value of 78.8%. (4) Conclusions: 99mTc-EDDA/HYNIC-TOC, a receptor-based radiopharmaceutical, could represent a competitor for 68Ga-labeled peptides in the diagnosis and management of patients with gastroenteropancreatic neuroendocrine tumors. Our results show a lower sensitivity (90.5%) than 68Ga-DOTA-peptides, but with great specificity, accuracy, positive, and negative predictive values.

Biology of Cancer and PET Imaging: Pictorial Review

Development and spread of cancer is a multi-step and complex process which involves number of alterations, interactions and molecular networks. PET imaging is closely related with biology of cancer as it detects the cancer based on biological and pathological changes in tumor cells and tumor microenvironment. In this review article, biology of development and spread of cancer and role of PET imaging in Oncology was summarized and supported with various PET images demonstrating cancer spread patterns.

Discordance between Histopathological grading and Dual Tracer PET-CT findings (68Ga-DOTATATE and FDG) in metastatic Neuroendocrine Neoplasms and outcome of 177Lu-DOTATATE PRRT: does in-vivo molecular PET imaging perform better from 'prediction of tumour biology' viewpoint?

Background and Aim: Discordance between histopathological grading and dual tracer PET-CT (⁶⁸Ga-DOTATATE and FDG) findings in neuroendocrine tumours (NETs), though not typical, can be encountered in real-world scenario. The aim of this study was to assess patients with discordance between WHO 2017 grade predicted molecular PET-CT imaging and the actual dual tracer PET-CT findings (by exploring their histopathological, immunohistochemical and molecular imaging characteristics), with a view to identifying the prognostic determinants effecting outcome in a peptide receptor radionuclide therapy (PRRT) set-up. Methods: Thirty six patients of histopathologically proven inoperable, locally advanced/metastatic NETs, referred for PRRT were included in this study. The cohort was divided into two broad population groups: (a) those with discordance (between WHO 2017 grade predicted molecular imaging and the dual tracer PET-CT findings) and (b) control (showing both FDG and ⁶⁸Ga-DOTATATE uptake). The cohort was divided based on dual tracer PET-CT into: (i) metabolically FDG non-avid and SSTR expressing tumors, (ii) metabolically active and non-⁶⁸Ga-DOTATATE concentrating (SSTR expressing) and (iii) matched imaging characteristics with WHO 2017 grading system (showing both FDG and ⁶⁸Ga-DOTATATE concentrating disease) for statistical analysis. Statistical analyses were done on SPSS 23.0. Descriptive statistics was used to analyze categorical data, multivariate analysis was used to assess the correlation between different variables with progression free survival (PFS) and overall survival (OS). Kaplan-Meier was used for survival analysis to calculate median survival and to analyze the survival based on WHO 2017 grading and dual tracer PET. Cox proportional hazards regression analysis was used to determine predictors of survival (OS and PFS). Results: In the entire cohort (n = 36), 24 patients (66.7%) showed discordance whereas 12 patients (33.3%) were in the control group. Among the patients showing discordance: 14 patients (38.9%) had metabolically inactive and SSTR expressing disease and remaining 10 patients (27.8%) had FDG concentrating and SSTR non-expressing disease. Those in the control group, 12 patients (33.3%) had intermediate grade NETs and showed matched (⁶⁸Ga-DOTATATE and FDG concentrating lesions) disease. Multivariate analysis in patients with discordant findings demonstrated significant correlation of dual tracer PET with overall survival while no significant correlation could be established between WHO grade and overall survival in the discordant subgroups. No significant correlation could be appreciated between PFS and either dual tracer PET or WHO grading. The Kaplan-Meier survival analysis and Cox proportional hazards regression analysis demonstrated dual tracer PET-CT imaging to be significant prognostic determinant and predictor of outcome respectively. Conclusion: In summary, in NET patients with discordance between the two parameters, dual tracer PET-CT with FDG and ⁶⁸Ga-DOTATATE performed better than WHO grading, differentiation status and immunohistochemistry in prognosticating and predicting outcome.

Liver: glucose metabolism and 18F-fluorodeoxyglucose PET findings in normal parenchyma and diseases

Liver has a complex and unique energy metabolism and plays a major role in glucose homeostasis. Liver is the main control center for glycogenesis, glycogenolysis, glycolysis and gluconeogenesis which are essential to provide energy for other tissues. Liver meets its own energy need from various sources which is mainly glucose in the fed state and fatty acids in the fasting state. In this review article, we will mainly describe the glucose metabolism of the liver, effect of various factors on 18F-fluorodeoxyglucose (FDG) activity/uptake in the normal liver and 18F- FDG positron emission tomography (PET) uptake patterns in various malignant and benign liver pathologies. Brief information on metabolomics profiling analyses in liver disorders will also be provided.

Added value of [68Ga]Ga-DOTA-TOC PET/CT for characterizing pancreatic neuroendocrine neoplasms: a comparison with contrast-enhanced CT and/or MRI in a large study cohort

OBJECTIVES

To investigate an additional value of [⁶⁸Ga]Ga-DOTA-TOC PET/CT for characterizing suspected pancreatic neuroendocrine neoplasms (NENs) in a large study cohort.

METHODS

This retrospective study included 167 patients who underwent [⁶⁸Ga]Ga-DOTA-TOC PET/CT for suspected pancreatic NENs detected by contrast-enhanced CT (n = 153) and/or MRI (n = 85). Two board-certified radiologists independently reviewed CT and/or MRI as well as [⁶⁸Ga]Ga-DOTA-TOC PET/CT and scored the probability of NEN on a 5-point scale. Radiologists' diagnostic performances with and without [⁶⁸Ga]Ga-DOTA-TOC PET/CT were compared using pathologic findings as the standard of reference.

RESULTS

All 167 patients were pathologically diagnosed with NENs (n = 131) or non-NENs (n = 36) by surgery (n = 93) or biopsy (n = 74). The non-NEN group included focal pancreatitis (n = 7), gastrointestinal stromal tumor (n = 6), serous cystadenoma (n = 5), metastatic renal cell carcinoma (n = 4), intrapancreatic accessory spleen (n = 4), ductal adenocarcinoma (n = 3), solid pseudopapillary neoplasm (n = 2), intraductal papillary mucinous carcinoma (n = 1), adenosquamous carcinoma (n = 1), schwannoma (n = 1), paraganglioma (n = 1), and solitary fibrous tumor (n = 1). Radiologists' diagnostic performance significantly improved after the addition of [⁶⁸Ga]Ga-DOTA-TOC PET/CT (AUC of CT: 0.737 vs. 0.886 for reviewer 1 [p = 0.0004]; 0.709 vs. 0.859 for reviewer 2 [p = 0.0002], AUC of MRI: 0.748 vs. 0.872 for reviewer 1 [p = 0.023]; 0.670 vs. 0.854 for reviewer 2 [p = 0.001]). [⁶⁸Ga]Ga-DOTA-TOC PET/CT significantly improved sensitivity (CT: 87.4% vs. 96.6% for reviewer 1 [p = 0.001]; 74.8% vs. 92.5% for reviewer 2 [p = 0.0001], MRI: 86.9% vs. 98.4% for reviewer 1 [p = 0.016]; 70.5% vs. 91.8% for reviewer 2 [p = 0.002]).

CONCLUSIONS

[⁶⁸Ga]Ga-DOTA-TOC PET/CT provided an additional value over conventional CT or MRI for the characterization of suspected pancreatic NENs.

KEY POINTS

• [⁶⁸Ga]Ga-DOTA-TOC PET/CT could provide additional value over conventional CT and/or MRI for the exact characterization of suspected pancreatic NENs by increasing AUC values and sensitivity. • Diagnostic improvement was significant, especially in NENs showing an atypical enhancement pattern. • The inter-observer agreement was improved when [⁶⁸Ga]Ga-DOTA-TOC PET/CT was added to CT and/or MRI.

Prognostic value of a three-scale grading system based on combining molecular imaging with 68Ga-DOTATATE and 18F-FDG PET/CT in patients with metastatic gastroenteropancreatic neuroendocrine neoplasias

We investigated on the added prognostic value of a three-scale combined molecular imaging with ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET/CT, (compared to Ki-67 based histological grading), in gastroenteropancreatic neuroendocrine neoplasia patients. 85 patients with histologically proven metastatic gastroenteropancreatic neuroendocrine neoplasias, who underwent combined PET/CT imaging were retrospectively evaluated. Highest Ki-67 value available at time of ¹⁸F-FDG PET/CT was recorded. Patients were classified according to World Health Organization/European Neuroendocrine Tumor Society histological grades (G1, G2, G3) and into three distinct imaging categories (C1: all lesions are ¹⁸F-FDG negative/⁶⁸Ga-DOTATATE positive, C2: patients with one or more ¹⁸F-FDG positive lesions, all of them ⁶⁸Ga-DOTATATE positive, C3: patients with one or more ¹⁸F-FDG positive lesions, at least one of them ⁶⁸Ga-DOTATATE negative). The primary endpoint of the study was Progression-Free Survival, assessed from the date of ¹⁸F-FDG PET/CT to the date of radiological progression according to Response Evaluation Criteria In Solid Tumors version 1.1. Classification according to histological grade did not show significant statistical difference in median Progression-Free Survival between G1 and G2 but was significant between G2 and G3 patients. In contrast, median Progression-Free Survival was significantly higher in C1 compared to C2 and in C2 compared to C3 patients, revealing three distinctive imaging categories, each with highly distinctive prognosis. Our three-scale combined ⁶⁸Ga-DOTATATE/¹⁸F-FDG PET imaging classification holds high prognostic value in patients with metastatic gastroenteropancreatic neuroendocrine neoplasias.

Prognostic and predictive value of nuclear imaging in endocrine oncology

In the last few years, the role and use of medical technologies in (neuro)endocrine oncology has greatly evolved allowing not only important diagnostic information but also prognostic stratification in different clinical situations. The terms "prognostic" and "predictive" are commonly used to describe the relationships between biomarkers and patients' clinical outcomes but have quite different meaning. The present work discusses the prognostic and predictive value of nuclear medicine imaging. It critically reviews the clinical significance and potential impact of molecular examinations on follow-up and therapeutic strategies in patients with neuroendocrine neoplasms, thyroid tumors, and adrenal malignancies.

The multidisciplinary team for gastroenteropancreatic neuroendocrine tumours: the radiologist's challenge

Background

Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) are a heterogeneous group of tumours. An effective diagnosis requires a multimodal approach that combines evaluation of clinical symptoms, hormonelevels, radiological and nuclear imaging, and histological confirmation. Imaging plays a critical role in NETs diagnosis, prognosis and management, so the radiologists are important members of the multidisciplinary team. During diagnostic work-up two critical issues are present: firstly the need to identify tumor presence and secondly to define the primary site and assess regional and distant metastases.

Conclusions

The most appropriate imaging technique depends on the type of neuroendocrine tumour and the availability of specialized imaging techniques and expertise. There is no general consensus on the most efficient imaging pathway, reflecting the challenge in reliably detection of these tumours.

Novel PET tracers: added value for endocrine disorders

Nuclear medicine has been implicated in the diagnosis and treatment of endocrine disorders for several decades. With recent development of PET tracers, functional imaging now plays a major role in endocrine tumors enabling with high performance to their localization, characterization, and staging. Besides ¹⁸F-FDG, which may be used in the management and follow-up of endocrine tumors, new tracers have emerged, such as ¹⁸F-DOPA for neuroendocrine tumors (NETs) (medullary thyroid carcinoma, pheochromocytomas and paragangliomas and well-differentiated NETs originating from the midgut) and ¹⁸F-Choline in the field of primary hyperparathyroidism. Moreover, some peptides such as somatostatin analogs can also be used for peptide receptor radionuclide therapy. In this context, Gallium-68 labeled somatostatin analogs (⁶⁸Ga-SSA) can help to tailor therapeutic choices and follow the response to treatment in the so-called "theranostic" approach. This review emphasizes the usefulness of these three novel PET tracers (¹⁸F-Choline, ¹⁸F-FDOPA, and ⁶⁸Ga-SSA) for primary hyperparathyroidism and neuroendocrine tumors.

What Is New in the 2017 World Health Organization Classification and 8th American Joint Committee on Cancer Staging System for Pancreatic Neuroendocrine Neoplasms?

The diagnosis and management of pancreatic neuroendocrine neoplasms (NENs) have evolved significantly in recent years. There are several diagnostic and therapeutic challenges and controversies regarding the management of these lesions. In this review, we focus on the recent significant changes and controversial issues regarding the diagnosis and management of NENs and discuss the role of imaging in the multidisciplinary team approach.

Clinical application of 99mTc-HYNIC-TOC SPECT/CT in diagnosing and monitoring of pancreatic neuroendocrine neoplasms

OBJECTIVE

Our aim of this research was to determine the value of SPECT/CT with ^99mTc-HYNIC-TOC for evaluation of the pancreatic masses which were suspected as neuroendocrine neoplasms and follow-up of patients with pancreatic neuroendocrine neoplasms.

METHODS

We retrospectively analyzed 184 patients who performed ^99mTc-HYNIC-TOC SPECT/CT. All the patients were divided into two groups: one for assessment of diagnostic efficiency for pancreatic suspected masses (n = 140) and another for monitoring recurrence after surgery (n = 44). The image findings acquired at 2 h postinjection were compared to final diagnoses from pathological results and clinical follow-up. Then, the correlation between ratios of tumor-to-background (TBR) and tumor grade was analyzed.

RESULTS

In group 1, 95/140 (67.9%) patients were confirmed as neuroendocrine neoplasms including 85 neuroendocrine tumors and 10 neuroendocrine carcinomas. Patient-based analysis showed that the sensitivity, specificity and accuracy of diagnosing neuroendocrine neoplasms with SPECT/CT were 81.1, 84.4 and 82.1%. There was significant difference of TBRs among G1, G2 and G3 (F = 3.175, P = 0.048). In group 2, 22/44 (50.0%) patients occurred metastasis mainly in liver. The sensitivity, specificity and accuracy of monitoring recurrence were 87.0, 100 and 93.2%.

CONCLUSIONS

^99mTc-HYNIC-TOC SPECT/CT is a reliable method of diagnosing and monitoring of pancreatic neuroendocrine neoplasms, especially neuroendocrine tumors.

Treatment challenges in and outside a specialist network setting: Pancreatic neuroendocrine tumours

Pancreatic Neuroendocrine Neoplasms comprise a group of rare tumours with special biology, an often indolent behaviour and particular diagnostic and therapeutic requirements. The specialized biochemical tests and radiological investigations, the complexity of surgical options and the variety of medical treatments that require individual tailoring, mandate a multidisciplinary approach that can be optimally achieved through an organized network. The present study describes currents concepts in the management of these tumours as well as an insight into the challenges of delivering the pathway in and outside a Network.

Role of Combined 68Ga-DOTATOC and 18F-FDG Positron Emission Tomography/Computed Tomography in the Diagnostic Workup of Pancreas Neuroendocrine Tumors: Implications for Managing Surgical Decisions

OBJECTIVES

Ga-DOTATOC (Ga) positron emission tomography (PET)/computed tomography (CT) is recommended in the workup of pancreas neuroendocrine tumors (PanNETs); evidence suggests that F-FDG (F) PET/CT can also provide prognostic information. Aims of this study were to assess the role of combined Ga- and F-PET/CT in the evaluation of grade (G) 1-2 PanNETs and to test the correlation between F-PET/CT positivity and tumor grade.

METHODS

Preoperative Ga- and F-PET/CT of 35 patients with surgically resected G1-2 PanNETs were evaluated. For grading, the 2010 World Health Organization Classification was used; an ancillary analysis with Ki67 cutoffs at 5% to 20% was conducted. Correlation between F-PET/CT positivity (SUVmax > 3.5) and grade was assessed.

RESULTS

Of 35 PanNETs, 28.6% and 71.4% were G1 and G2 as per World Health Organization. Ga-PET/CT showed high sensitivity (94.3%) in detecting G1-2 PanNETs. F-PET/CT was positive in 20% and 76% G1 and G2 tumors (P = 0.002). F-PET/CT identified G2 PanNETs with high positive predictive value (PPV, 90.5%). F-PET/CT correlated with tumor grade also in the ancillary analysis (P = 0.009).

CONCLUSIONS

The high sensitivity of Ga-PET/CT in NET detection is known. The high PPV of F-PET/CT in the identification of G2 forms suggests its potential role in PanNETs prognostication and risk stratification.

Octreoscan Versus FDG-PET for Neuroendocrine Tumor Staging: A Biological Approach

BACKGROUND

Clinicians may order Octreoscan or positron emission tomography (PET) scan for staging patients with neuroendocrine tumors (NETs). (111)In-Octreoscan (Octreoscan) identifies tumors by radiolabeled targeting of somatostatin receptors, while 18F-fluorodeoxyglucose-positron emission tomography ((18)FDG-PET) measures differential tissue glucose transport. We assessed the sensitivity of both nuclear imaging modalities with pathologic correlation to define the best initial choice for NET staging after standard cross-sectional imaging.

METHODS

We identified all patients diagnosed with NETs of gastrointestinal or pancreatic origin who underwent nuclear imaging staging by Octreoscan and/or PET from 2000 to 2013. Imaging results were correlated with tumor differentiation and grade of pathology specimens.

RESULTS

Imaging and pathology results were identified for 153 patients. Of these, 131 underwent Octreoscan, 43 underwent PET, and 21 patients had both performed. Overall sensitivity of Octreoscan and PET for NET detection was similar (77 vs. 72 %; p = not significant). For well-differentiated NETs, Octreoscan (n = 124) demonstrated sensitivity of 80 vs. 60 % (p = 0.28) for PET (n = 30). For poorly-differentiated NETs, Octreoscan (n = 7) proved significantly less sensitive than PET (n = 13) (57 vs. 100 %; p = 0.02). The sensitivity of Octreoscan versus PET varied similarly when analyzed by WHO tumor grade: Grade 1 (79 vs. 52 %; p = 0.16), Grade 2 (85 vs. 86 %; p = not significant), and Grade 3 (57 vs. 100 %; p = 0.02).

CONCLUSIONS

Tumor differentiation can be used to guide selection of nuclear imaging modalities for staging gastrointestinal and pancreatic NETs. Octreoscan appears more sensitive than (18)FDG-PET for well-differentiated NETs, whereas (18)FDG-PET demonstrates superior sensitivity for poorly-differentiated NETs.

18F-fluorodihydroxyphenylalanine PET/CT in patients with neuroendocrine tumors of unknown origin: relation to tumor origin and differentiation

This work was performed to evaluate the performance of (18)F-fluorodihydroxyphenylalanine ((18)F-FDOPA) PET/CT in detecting primary neuroendocrine tumors (NETs) occult on morphologic and functional imaging, in relation to tumor origin and differentiation.

METHODS

A retrospective study of NET patients who were investigated with (18)F-FDOPA PET/CT imaging in 2 academic endocrine tumor centers was conducted. Only patients with negative conventional and somatostatin receptor scintigraphy (SRS) results were studied.

RESULTS

Twenty-seven patients were evaluated with (18)F-FDOPA PET/CT, 23 at their initial staging and 4 during their follow-up. The primary occult NET was localized by (18)F-FDOPA PET/CT in 12 patients (overall sensitivity, 44%; 52% in patients evaluated at initial diagnosis), leading to tumor resection in all cases. The primary tumors were distributed and graded as follows: 1 duodenum G2 lesion, 7 ileum G2 lesions, 2 terminal ileum G1 lesions, 1 pancreas G2 lesion, and 1 gallbladder G3 lesion. Patients with positive (18)F-FDOPA PET/CT results had higher values of serum chromogranin A (100% vs. 20%, P = 0.0003), serotonin, or urinary 5-hydroxyindolacetic acid (83% vs. 20%, P = 0.003). Two false-negative results were related to poorly differentiated duodenal and prostatic NETs (G3). (18)F-FDOPA PET/CT showed more metastatic anatomic regions than SRS in 17 patients.

CONCLUSION

(18)F-FDOPA PET appears to be a sensitive functional imaging tool for the detection of primary NETs occult on SRS, especially tumors with a well-differentiated pattern and serotonin secretion.

Update on the management of gastroenteropancreatic neuroendocrine tumors with emphasis on the role of imaging

OBJECTIVE

The purposes of this article are to review the current management of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) based on the 2012 National Comprehensive Cancer Network guidelines and to describe the role of imaging in a multidisciplinary approach.

CONCLUSION

The management of GEP-NETs has become complex, requiring a multidisciplinary approach. The World Health Organization classification of GEP-NETs has been revised; the U.S. Food and Drug Administration has approved molecular targeted agents (sunitinib, everolimus) for the treatment of pancreatic NETs; and the National Comprehensive Cancer Network clinical practice guidelines have been updated.