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

The role of combined FDG and SST PET/CT in neuroendocrine tumors

Somatostatin receptor (SST) positron emission tomography with computed tomography (PET/CT) is the gold standard for functional imaging of neuroendocrine tumors (NETs), but FDG PET/CT is increasingly recognized for its prognostic value, particularly for higher-grade NETs and to detect disease heterogeneity. Despite the established role of pathological grading, clinical heterogeneity within the tumor burden often complicates accurate prognostication. Evidence suggests FDG PET/CT can outperform WHO grading in predicting outcomes by identifying aggressive, undifferentiated tumor clones that influence long-term prognosis and treatment decisions. Several grading systems integrating both SST and FDG PET/CT have been proposed to better capture tumor heterogeneity and guide clinical management. Studies demonstrate that FDG PET/CT can influence management in a significant subset of patients, although variably reported. Its use remains variable across centers, also affected by different reimbursement policies and local clinical practices. This review explores the indications to FDG PET/CT in NET and the clinical impact of combined SST and FDG PET/CT imaging.

Gastroenteropancreatic neuroendocrine neoplasms: current development, challenges, and clinical perspectives

Neuroendocrine neoplasms (NENs) are highly heterogeneous and potentially malignant tumors arising from secretory cells of the neuroendocrine system. Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are the most common subtype of NENs. Historically, GEP-NENs have been regarded as infrequent and slow-growing malignancies; however, recent data have demonstrated that the worldwide prevalence and incidence of GEP-NENs have increased exponentially over the last three decades. In addition, an increasing number of studies have proven that GEP-NENs result in a limited life expectancy. These findings suggested that the natural biology of GEP-NENs is more aggressive than commonly assumed. Therefore, there is an urgent need for advanced researches focusing on the diagnosis and management of patients with GEP-NENs. In this review, we have summarized the limitations and recent advancements in our comprehension of the epidemiology, clinical presentations, pathology, molecular biology, diagnosis, and treatment of GEP-NETs to identify factors contributing to delays in diagnosis and timely treatment of these patients.

Tumour Heterogeneity and the Consequent Practical Challenges in the Management of Gastroenteropancreatic Neuroendocrine Neoplasms

Tumour heterogeneity is a common phenomenon in neuroendocrine neoplasms (NENs) and a significant cause of treatment failure and disease progression. Genetic and epigenetic instability, along with proliferation of cancer stem cells and alterations in the tumour microenvironment, manifest as intra-tumoural variability in tumour biology in primary tumours and metastases. This may change over time, especially under selective pressure during treatment. The gastroenteropancreatic (GEP) tract is the most common site for NENs, and their diagnosis and treatment depends on the specific characteristics of the disease, in particular proliferation activity, expression of somatostatin receptors and grading. Somatostatin receptor expression has a major role in the diagnosis and treatment of GEP-NENs, while Ki-67 is also a valuable prognostic marker. Intra- and inter-tumour heterogeneity in GEP-NENS, however, may lead to inaccurate assessment of the disease and affect the reliability of the available diagnostic, prognostic and predictive tests. In this review, we summarise the current available evidence of the impact of tumour heterogeneity on tumour diagnosis and treatment of GEP-NENs. Understanding and accurately measuring tumour heterogeneity could better inform clinical decision making in NENs.

Role of [18F]FDG PET/CT in the management of G1 gastro-entero-pancreatic neuroendocrine tumors

PURPOSE

Since the role of [18F]FDG PET/CT in low-grade gastroenteropancreatic (GEP) neuroendocrine neoplasia (NET) is not well established, this study was aimed to evaluate the role of [18F]FDG PET/CT in grade 1 (G1) GEP-NETs.

METHODS

This is a retrospective study including patients with G1 GEP-NETs who underwent [18F]FDG PET/CT.

RESULTS

55 patients were evaluated, including 24 (43.6%) with pancreatic NETs and 31 (56.4%) with gastrointestinal NETs. At the time of diagnosis, 28 (51%) patients had metastatic disease, and 50 (91%) patients were positive by 68-Ga sstr PET/CT. Overall, 27 patients (49%) had positive findings on [18F]FDG PET/CT. Following [18F]FDG PET/CT, therapeutic management was modified in 29 (52.7%) patients. Progression-free survival was longer in patients with negative [18F]FDG PET/CT compared with positive [18F]FDG PET/CT (median PFS was not reached and 24 months, respectively, p = 0.04). This significance was particularly evident in the pancreatic group (p = 0.008).

CONCLUSIONS

Despite having low proliferative activity, approximately half of GEP-NETs G1 showed positive [18F]FDG PET/CT, with a corresponding negative impact on patients' clinical outcomes. These data are in favor of a more "open" attitude toward the potential use of [18F]FDG PET/CT in the diagnostic work-up of G1 GEP-NETs, which may be used in selected cases to detect those at higher risk for an unfavorable disease course.

The Potential Prognostic Value of Dual-Imaging PET Parameters Based on 18F-FDG and 18F-OC for Neuroendocrine Neoplasms

Background

To identify parameters based on dual-imaging ¹⁸F-AlF-NOTA-octreotide (¹⁸F-OC) and 18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) for predicting the prognosis of neuroendocrine neoplasms (NENs).

Materials and Methods

Sixty-six patients (age: mean ± standard deviation (SD): 51.8 ± 11.8 years) who underwent both ¹⁸F-OC and ¹⁸F-FDG PET/CT imaging were enrolled in our retrospective study. The following PET parameters were measured: the maximum standardized uptake value (SUV_max) and the volumetric parameters—¹⁸F-OC SSR-derived tumor volume (TV) and somatostatin receptor expression (SRE, TV multiplied by the mean standardized uptake value (SUV_mean)) and the ¹⁸F-FDG-derived multiple tumor volume (MTV) and tumor lesion glycolysis (TLG). The NETPET grade based on dual-imaging PET images was assessed. Progression-free survival (PFS) was set as an endpoint. Univariate and multivariate survival analyses were performed for PET parameters and clinical tumor data.

Results

In the univariate survival analyses of clinical information, PFS was significantly associated with age (>45.5 vs ≤45.5, years, P < 0.034) and the presence of bone metastases (P = 0.04). Higher values for the ¹⁸F-FDG and ¹⁸F-OC volumetric parameters and the NETPET grade were adverse factors for PFS according to the dual-imaging PET parameters. In the multivariate survival analysis, the NETPET grade and SRE were predictors of PFS in NEN patients.

Conclusion

The NETPET grade is a potential noninvasive prognostic biomarker for NENs.

Treatment of Neuroendocrine Neoplasms with Radiolabeled Peptides-Where Are We Now

Peptide receptor radionuclide therapy (PRRT) has been one of the most successful and exciting examples of theranostics in nuclear medicine in recent decades and is now firmly embedded in many treatment algorithms for unresectable or metastatic neuroendocrine neoplasms (NENs) worldwide. It is widely considered to be an effective treatment for well- or moderately differentiated neoplasms, which express high levels of somatostatin receptors that can be selectively targeted. This review article outlines the scientific basis of PRRT in treatment of NENs and describes its discovery dating back to the early 1990s. Early treatments utilizing Indium-111, a γ-emitter, showed promise in reduction in tumor size and improvement in biochemistry, but were also met with high radiation doses and myelotoxic and nephrotoxic effects. Subsequently, stable conjugation of DOTA-peptides with β-emitting radionuclides, such as Yttrium-90 and Lutetium-177, served as a breakthrough for PRRT and studies highlighted their potential in eliciting progression-free survival and quality of life benefits. This article will also elaborate on the key trials which paved the way for its approval and will discuss therapeutic considerations, such as patient selection and administration technique, to optimize its use.

Role of Combined 68Ga DOTA-Peptides and 18F FDG PET/CT in the Evaluation of Gastroenteropancreatic Neuroendocrine Neoplasms

This review article summarizes the role of combined ⁶⁸Ga DOTA-peptides and ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in the evaluation of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). Patients with GEP-NENs can initially present themselves to a gastroenterologist or endocrinologist rather than cancer specialist; hence, it is vital for a wider group of clinicians to be familiar with the range of tests available for the evaluation of these patients. The role of PET scanning by using ⁶⁸Ga DOTA-peptides has a high sensitivity in the diagnosis of GEP-NENs and to guide patient selection for treatment with somatostatin analogues (SSA) and/or peptide receptor radionuclide therapy (PRRT). The loss of somatostatin receptor (SSTR) expression was found to be associated with an increased glucose metabolism in cells. However, the routine use of SSTR targeted radiotracers in combination with ¹⁸F-FDG to evaluate glucose utilization in GEP-NENs is still debatable. In our opinion, in patients with NENs, ¹⁸F-FDG PET should be performed in the case of a negative or slightly positive ⁶⁸Ga DOTA-peptides PET scan for assessing the dedifferentiation status, to guide correct therapeutic strategy and to evaluate the prognosis. The approach of combined receptor and metabolic imaging can improve diagnostic accuracy, especially considering the heterogeneity of these lesions. Therefore, ⁶⁸Ga DOTA-peptides and ¹⁸F-FDG PET should be considered complementary in patients with GEP-NENs.

Current status and future prospects of PET-imaging applications in patients with gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs)

Gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs) represent a heterogeneous group of rare neoplasms with increasing incidence over the last decades. Localization of GEP-NETs and their metastases is a vital component for the implementation of accurate and patient-tailored treatment strategies. Addressing this challenge requires the employment of multidisciplinary imaging approaches, with hybrid positron emission tomography/computed tomography (PET/CT) imaging techniques standing at the forefront of this effort. GEP-NETs exhibit several pathophysiologic characteristics, which can serve as highly specific molecular targets that can be effectively visualized and quantified by means of PET-radiopharmaceuticals, facilitating diagnosis, accurate staging and efficient monitoring of treatment response. Furthermore, the capability for whole-body, in-vivo, non-invasive characterization of the molecular heterogeneity of the disease, provides strong prognostic information, while enabling the selection of patients suitable for precision-based theranostic approaches. The dual tracer (¹⁸F-FDG & ⁶⁸Ga-DOTA-peptides) PET/CT imaging approach is the current optimal diagnostic imaging strategy, since it enables tumor localization, accurate staging, non-invasive whole-body total tumor burden characterization of disease heterogeneity, while providing strong prognostic information and guidance towards treatment strategy. Moreover, ⁶⁴Cu-DOTATATE has been recently approved by FDA for SSTRs positive NETs, promising substantial diagnostic and logistical benefits. Furthermore, ¹⁸F-DOPA offers diagnostic capabilities for serotonin-secreting GEP-NETs which are not characterized by cell-surface over-expression of somatostatin receptors (SSTRs) and cannot be seen on morphological imaging. In addition, PET/CT with agents targeting the expression of glucagon-like peptide-1 receptor (GLP-R1) should be considered in cases of clinical suspicion for insulinomas that cannot be detected by morphological imaging or STTRs PET/CT imaging.

Correlation of 68Ga-DOTATATE uptake on PET/CT with pathologic features of cellular proliferation in neuroendocrine neoplasms

OBJECTIVE

68Ga-DOTATATE positron emission tomography/computed tomography (PET/CT) is a useful tool for diagnosing and staging neuroendocrine neoplasms (NEN). Unlike other PET tracers like FDG, the meaningfulness and use of standardized uptake values (SUVs) of 68Ga-DOTATATE is not well-established. This study aimed to determine if a correlation exists between intensity of 68Ga-DOTATATE uptake and markers of cellular proliferation.

METHODS

This retrospective study included 79 patients with positive 68Ga-DOTATATE PET/CT and Ki-67 and/or mitotic index (MI) available on pathology report. SUVmax of the most intense lesion and the most intense organ-matched lesion were determined. Demographics and pathology results for Ki-67 and MI were collected from the electronic medical record. Correlations and trends for correlations of SUVmax to Ki-67 and MI were performed using Kruskal-Wallis and Cuzick trend tests.

RESULTS

A trend for an association between SUVmax and Ki-67 grade was found; median SUVmax of Ki-67 < 3%, 3-20%, and > 20% was 35.2, 31.8, and 12.8 (p = 0.077), respectively. There was also a trend between SUVmax and Ki-67 categories in organ-matched lesions (p = 0.08). The median organ-matched SUVmax of MI < 2, 2-20, and > 20 lesions was 34.2, 18, and 21.7, respectively, (Cuzick trend test p = 0.066). The median SUVmax for small bowel, pancreatic, and other primary locations was 27.6, 46.9, and 9.3 (p < 0.01), respectively.

CONCLUSIONS

The association between 68Ga-DOTATATE SUVmax, histologic grade, and primary site of NEN demonstrates its potential use for prognostication, or potentially as a surrogate for histologic grading when biopsy is not possible.

Imaging of Pancreatic Neuroendocrine Neoplasms

Pancreatic neuroendocrine neoplasms (panNENs) represent the second most common pancreatic tumors. They are a heterogeneous group of neoplasms with varying clinical expression and biological behavior, from indolent to aggressive ones. PanNENs can be functioning or non-functioning in accordance with their ability or not to produce metabolically active hormones. They are histopathologically classified according to the 2017 World Health Organization (WHO) classification system. Although the final diagnosis of neuroendocrine tumor relies on histologic examination of biopsy or surgical specimens, both morphologic and functional imaging are crucial for patient care. Morphologic imaging with ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI) is used for initial evaluation and staging of disease, as well as surveillance and therapy monitoring. Functional imaging techniques with somatostatin receptor scintigraphy (SRS) and positron emission tomography (PET) are used for functional and metabolic assessment that is helpful for therapy management and post-therapeutic re-staging. This article reviews the morphological and functional imaging modalities now available and the imaging features of panNENs. Finally, future imaging challenges, such as radiomics analysis, are illustrated.

Multiple endocrine neoplasia type 1 (MEN-1) and neuroendocrine neoplasms (NENs)

Neuroendocrine neoplasms (NENs) are relatively rare neoplasms with 6.4-times increasing age-adjusted annual incidence during the last four decades. NENs arise from neuroendocrine cells, which release hormones in response to neuronal stimuli and they are distributed into organs and tissues. The presentation and biological behaviour of the NENs are highly heterogeneous, depending on the organ. The increased incidence is mainly due to increased awareness and improved detection methods both in the majority of sporadic NENs (non-inherited), but also the inherited groups of neoplasms appearing in at least ten genetic syndromes. The most important one is multiple endocrine neoplasia type 1 (MEN-1), caused by mutations in the tumour suppressor gene MEN1. MEN-1 has been associated with different tumour manifestations of NENs e.g. pancreas, gastrointestinal tract, lungs, thymus and pituitary. Pancreatic NENs tend to be less aggressive when arising in the setting of MEN-1 compared to sporadic pancreatic NENs. There have been very important improvements over the past years in both genotyping, genetic counselling and family screening, introduction and validation of various relevant biomarkers, as well as newer imaging modalities. Alongside this development, both medical, surgical and radionuclide treatments have also advanced and improved morbidity, quality of life and mortality in many of these patients. Despite this progress, there is still space for improving insight into the genetic and epigenetic factors in relation to the biological mechanisms determining NENs as part of MEN-1. This review gives a comprehensive update of current evidence for co-occurrence, diagnosis and treatment of MEN-1 and neuroendocrine neoplasms and highlight the important progress now finding its way to international guidelines in order to improve the global management of these patients.

Collision of Solid Pseudopapillary Tumor and Neuroendocrine Tumor of the Pancreas on 18F-FDG PET/CT

ABSTRACT

We report a rare case of pancreatic collision tumor of solid pseudopapillary tumor and neuroendocrine tumor in a 43-year-old woman. A pancreatic mass was found by abdominal ultrasound. A mainly cystic mass with solid component progressive enhancement was revealed using abdominal enhanced CT. Staging 18F-FDG PET/CT demonstrated a pancreatic tail mass with an increased uneven 18F-FDG uptake. Distal pancreatectomy was performed. Postoperatively, the mass was diagnosed as pancreatic collision tumor of solid pseudopapillary tumor and neuroendocrine tumor.

[18F]FDG-PET/CT and long-term responses to everolimus in advanced neuroendocrine neoplasia

PURPOSE

This study aims to identify in patients with neuroendocrine neoplasia (NEN) the potential correlation between FDG-PET findings and responses to everolimus therapy to identify predictors of long-term efficacy.

METHODS

Retrospective analysis of patients with sporadic, advanced, progressive NEN treated with everolimus was performed based on the available data on FDG-PET patients obtained before commencing therapy. Data are expressed as the median (25-75th IQR). Risk factor analysis and survival analysis were performed by logistic regression and Cox proportional hazard regression and the determination of Kaplan-Meier curves, as appropriate.

RESULTS

Sixty-six patients were evaluated (NET G1 19.7%, NET G2 75.7%, and NET G3 4.6%), including 45.4% with positive FDG-PET findings. Overall, disease stabilization and a partial response were achieved for 71.2% and 6% of patients, respectively. A long-term response (> 24 months) was observed in 33% of patients. Ki67 was the only predictor of tumor progression (p = 0.03). No significant difference in clinical outcomes was observed between patients with positive or negative FDG-PET findings (median PFS was 24 months and 18 months, respectively, p = 0.337; the disease control rate was 83.3% and 70%, respectively, p = 0.245).

CONCLUSIONS

Everolimus is a valid therapeutic option for advanced, progressive, well-differentiated NEN, even in patients with positive FDG-PET findings.

Prospective study of dynamic whole-body 68Ga-DOTATOC-PET/CT acquisition in patients with well-differentiated neuroendocrine tumors

To present the feasibility of a dynamic whole-body (DWB) ⁶⁸Ga-DOTATOC-PET/CT acquisition in patients with well-differentiated neuroendocrine tumors (WD-NETs). Sixty-one patients who underwent a DWB ⁶⁸Ga-DOTATOC-PET/CT for a histologically proven/highly suspected WD-NET were prospectively included. The acquisition consisted in single-bed dynamic acquisition centered on the heart, followed by the DWB and static acquisitions. For liver, spleen and tumor (1–5/patient), Ki values (in ml/min/100 ml) were calculated according to Patlak's analysis and tumor-to-liver (TLR-Ki) and tumor-to-spleen ratios (TSR-Ki) were recorded. Ki-based parameters were compared to static parameters (SUVmax/SUVmean, TLR/TSRmean, according to liver/spleen SUVmean), in the whole-cohort and according to the PET system (analog/digital). A correlation analysis between SUVmean/Ki was performed using linear and non-linear regressions. Ki-liver was not influenced by the PET system used, unlike SUVmax/SUVmean. The regression analysis showed a non-linear relation between Ki/SUVmean (R² = 0.55,0.68 and 0.71 for liver, spleen and tumor uptake, respectively) and a linear relation between TLRmean/TLR-Ki (R² = 0.75). These results were not affected by the PET system, on the contrary of the relation between TSRmean/TSR-Ki (R² = 0.94 and 0.73 using linear and non-linear regressions in digital and analog systems, respectively). Our study is the first showing the feasibility of a DWB ⁶⁸Ga-DOTATOC-PET/CT acquisition in WD-NETs.

Update on gastroenteropancreatic neuroendocrine tumors

The incidence gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) has dramatically risen over the last three decades, probably due to the increased detection of asymptomatic lesions. The diagnostic work-up for patients with suspected GEP-NENs is based on conventional imaging, endoscopy, pathology, and functional imaging, including 68Gallium-DOTATATE PET and 18F-FDG PET. The choice of the best treatment strategy should be based on the evaluation of tumor-related features and patient's characteristics. A conservative management, consisting of active surveillance or endoscopic resection, has been advocated for patients with small, incidentally discovered, nonfunctioning tumors without features of aggressiveness. On the other hand, surgery with lymphadenectomy, also with a minimally invasive approach, represents the gold standard for the curative treatment of localized disease. Moreover, surgical resection plays an important role also in the context of a multimodal treatment strategy for patients with advanced GEP-NENs. Finally, a wide range of medical therapies, comprising somatostatin analogues, peptide receptor radionuclide therapy, target therapies and several chemotherapy regimens, can be offered to patients with advanced GEP-NENs not amenable of surgical resection, according to the biological and molecular features of their disease.

Dual-Tracer (68Ga-DOTATOC and 18F-FDG-)-PET/CT Scan and G1-G2 Nonfunctioning Pancreatic Neuroendocrine Tumors: A Single-Center Retrospective Evaluation of 124 Nonmetastatic Resected Cases

INTRODUCTION

The combined use of 68gallium (68Ga)-DOTA-peptides and 18fluorine-fluoro-2-deoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scans in the workup of pancreatic neuroendocrine tumors (PanNETs) is controversial. This study aimed at assessing both tracers' capability to identify tumors and to assess its association with pathological predictors of recurrence.

METHODS

Prospectively collected, preoperative, dual-tracer PET/CT scan data of G1-G2, nonmetastatic, PanNETs that underwent surgery between January 2013 and October 2019 were retrospectively analyzed.

RESULTS

The final cohort consisted of 124 cases. There was an approximately equal distribution of males and females (50.8%/49.2%) and G1 and G2 tumors (49.2%/50.8%). The disease was detected in 122 (98.4%) and 64 (51.6%) cases by 68Ga-DOTATOC and by 18F-FDG PET/CT scans, respectively, with a combined sensitivity of 99.2%. 18F-FDG-positive examinations found G2 tumors more often than G1 (59.4 vs. 40.6%; p = 0.036), and 18F-FDG-positive PanNETs were larger than negative ones (median tumor size 32 mm, interquartile range [IQR] 21 vs. 26 mm, IQR 20; p = 0.019). The median Ki67 for 18F-FDG-positive and -negative examinations was 3 (IQR 4) and 2 (IQR 4), respectively (p = 0.029). At least 1 pathological predictor of recurrence was present in 74.6% of 18F-FDG-positive cases (vs. 56.7%; p = 0.039), whereas this was not found when dichotomizing the PanNETs by their dimensions (≤/>20 mm). None of the 2 tracers predicted nodal metastasis. The receiver operating characteristic curve analysis showed that 18F-FDG uptake higher than 4.2 had a sensitivity of 49.2% and specificity of 73.3% for differentiating G1 from G2 (AUC = 0.624, p = 0.009).

CONCLUSION

The complementary adoption of 68Ga-DOTATOC and 18F-FDG tracers may be valuable in the diagnostic workup of PanNETs despite not being a game-changer for the management of PanNETs ≤20 mm.

Tumor Heterogenity in Gastro-Entero-Pancreatic Neuroendocrine Neoplasia

Owing to the rarity and the biological and clinical heterogeneity of gastroenteropancreatic neuroendocrine neoplasia (GEP NEN), the management of these patients may be challenging for physicians. This review highlights the specific features of GEP NEN with particular attention on the role of Ki67 heterogeneity, the potential prognostic role of novel radiological techniques, and the clinical usefulness of functional imaging, including 68Ga-DOTA-SST PET/CT and 18F-FDG PET/CT. Understanding these specific features may help to plan proper and tailored follow-up programs and therapeutic approaches.

Comparison of 68Ga-DOTANOC and 18F-FDG PET-CT Scans in the Evaluation of Primary Tumors and Lymph Node Metastasis in Patients With Rectal Neuroendocrine Tumors

BACKGROUND

Lymph node metastasis of rectal neuroendocrine tumors (RNETs) predicts poor prognosis. However, the assessment of lymph node metastasis remains a challenge. It has been reported that 68Ga-DOTANOC and 18F-FDG PET-CT scans could be employed in the work-up of rectal neuroendocrine tumors (RNETs). This study aimed to assess both tracers' ability to identify primary tumors and lymph node (LN) metastasis in RNETs.

METHODS

A total of 537 patients with RNETs were enrolled from January 2014 to January 2021. Both 68Ga-DOTANOC and 18F-FDG PET-CT scans were used to evaluate primary tumors and LN group metastasis. PET images were evaluated through visual and semiquantitative assessment. Receiver Operating Characteristics (ROC) curve analysis was used to investigate the performance of SUVmax of 68Ga-DOTANOC and 18F-FDG PET in predicting LN group metastasis.

RESULTS

Fifty-two patients with preoperative 68Ga-DOTANOC with 18F-FDG PET-CT scans underwent endoscopic biopsy or dissection of the primary tumor, while 11 patients underwent rectal surgery together with regional LN dissection. For primary tumors, 68Ga-DOTANOC had a sensitivity of 89.58% and a positive predictive value (PPV) of 95.56% through visual assessment, while 18F-FDG PET-CT showed 77.08% sensitivity and 97.37% PPV. For the prediction of LN group metastasis, 68Ga-DOTANOC PET-CT had 77.78% sensitivity and 91.67% specificity, while 18F-FDG PET-CT had 38.89% sensitivity and 100% specificity according to visual assessment. The area under the ROC curves (AUC) for 68Ga-DOTANOC PET/CT was 0.852 (95%CI:0.723-0.981) with an optimal SUVmax cut-off value of 2.25, while the AUC for 18F-FDG PET were 0.664 (95%CI:0.415-0.799) with an optimal SUVmax cut-off value of 1.05.

CONCLUSIONS

This study showed that 68Ga-DOTANOC PET-CT was a promising tool for detecting LN metastasis in RNETs with high sensitivity and specificity in visual assessment and semiquantitative assessment, which was better than 18F-FDG PET-CT.

Role of PET/CT and Therapy Management of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine neoplasms (panNENs) are heterogeneous neoplasms with neuroendocrine differentiation that show peculiar clinical and histomorphological features, with variable prognosis. In recent years, advances in knowledge regarding the pathophysiology and heterogeneous clinical presentation, as well as the availability of different diagnostic procedures for panNEN diagnosis and novel therapeutic options for patient clinical management, has led to the recognition of the need for an active multidisciplinary discussion for optimal patient care. Molecular imaging with positron emission tomography/computed tomography (PET/CT) has become indispensable for the management of panNENs. Several PET radiopharmaceuticals can be used to characterize either panNEN receptor expression or metabolism. The aim of this review is to offer an overview of all the currently used radiopharmaceuticals and of the new upcoming tracers for pancreatic neuroendocrine tumors (panNETs), and their clinical impact on therapy management. [68Ga]Ga-DOTA-peptide PET/CT (SSA-PET/CT) has high sensitivity, specificity, and accuracy and is recommended for the staging and restaging of any non-insulinoma well-differentiated panNEN cases to carry out detection of unknown primary tumor sites or early relapse and for evaluation of in vivo somatostatin receptors expression (SRE) to select patient candidates for peptide receptor radiometabolic treatment (PRRT) with 90Y or 177Lu and/or cold analogs. SSA-PET/CT also has a strong impact on clinical management, leading to a change in treatment in approximately a third of the cases. Its role for treatment response assessment is still under debate due to the lack of standardized criteria, even though some semiquantitative parameters seem to be able to predict response. [18F]FDG PET/CT generally shows low sensitivity in small growing and well-differentiated neuroendocrine tumors (NET; G1 and G2), while it is of utmost importance in the evaluation and management of high-grade NENs and also provides important prognostic information. When positive, [18F]FDG PET/CT impacts therapeutical management, indicating the need for a more aggressive treatment regime. Although FDG positivity does not exclude the patient from PRRT, several studies have demonstrated that it is certainly useful to predict response, even in this setting. The role of [18F]FDOPA for the study of panNET is limited by physiological uptake in the pancreas and is therefore not recommended. Moreover, it provides no information on SRE that has crucial clinical management relevance. Early acquisition of the abdomen and premedication with carbidopa may be useful to increase the accuracy, but further studies are needed to clarify its utility. GLP-1R agonists, such as exendin-4, are particularly useful for benign insulinoma detection, but their accuracy decreases in the case of malignant insulinomas. Being a whole-body imaging technique, exendin-PET/CT gives important preoperative information on tumor size and localization, which is fundamental for surgical planning as resection (enucleation of the lesion or partial pancreatic resection) is the only curative treatment. New upcoming tracers are under study, such as promising SSTR antagonists, which show a favorable biodistribution and higher tumor-to-background ratio that increases tumor detection, especially in the liver. [68Ga]pentixafor, an in vivo marker of CXCR4 expression associated with the behavior of more aggressive tumors, seems to only play a limited role in detecting well-differentiated NET since there is an inverse expression of SSTR2 and CXCR4 in G1 to G3 NETs with an elevation in CXCR4 and a decrease in SSTR2 expression with increasing grade. Other tracers, such as [68Ga]Ga-PSMA, [68Ga]Ga-DATA-TOC, [18F]SiTATE, and [18F]AlF-OC, are also under investigation.

CT texture analysis of liver metastases in PNETs versus NPNETs: Correlation with histopathological findings

PURPOSE

To compare CT and Texture features of liver metastases in Pancreatic Neuroendocrine Tumors (PNETs) and in Non-Pancreatic Neuroendocrine Tumors (NPNETs) according to tumor grading, overall survival (OS), time to progression (TTP) and Ki67 index.

METHODS

23 patients with PNETs and 25 patients with NPNETs affected by liver metastases were compared. The lesions were G1 and G2 according to WHO classification of tumors. Texture parameters (Mean, Standard Deviation, Entropy, Kurtosis, Skewness, Mean of Positive Pixel) at different spatial scale image filtration (SSF) were evaluated in both arterial and portal phase using a dedicated software for volumetric analysis. All CT images were acquired before the beginning of any medical treatment.

RESULTS

The following significant results (P < 0.05) were found: in the arterial phase for value of Skewness between PNETs G2 and NPNETs G2; in the portal phase between PNETs versus NPNETs, PNETs G1 versus NPNETs G1, PNETs G2 versus NPNETs G2; value of Mean in portal phase in PNETs vs NPNETs. Regarding PNETs, a P < 0.05 was found in: inverse correlation between Entropy and TTP; direct correlation between Mean and OS; correlating Kurtosis and high risk of death; correlating Skewness and low risk of death. Regarding NPNETs, P < 0.05 was found in: inverse correlation between Entropy and OS; correlating Entropy and high risk of dying.

CONCLUSIONS

This study shows that CT texture features are significantly different in PNETs from NPNETs. Additionally, textural features such as Entropy, Kurtosis and Skewness, were found to have significant correlation with higher mortality risk.

Role of Combined [68Ga]Ga-DOTA-SST Analogues and [18F]FDG PET/CT in the Management of GEP-NENs: A Systematic Review

Gastro-entero-pancreatic neuroendocrine neoplasia (GEP-NENs) are rare tumors, but their frequency is increasing. Neuroendocrine tumors normally express somatostatin (SST) receptors (SSTR) on cell surface, especially G1 and G2 stage tumors, but they can show a dedifferentiation in their clinical history as they become more aggressive. Somatostatin receptor imaging has previously been performed with a gamma camera using [111In]In or [99mTc]Tc-labelled compounds, while [68Ga]Ga-labelled compounds and PET/CT imaging has recently become the gold standard for the diagnosis and management of these tumors. Moreover, in the last few years 18F-fluorodeoxyglucose ([18F]FDG) PET/CT has emerged as an important tool to define tumor aggressiveness and give relevant prognostic information, particularly when coupled with [68Ga]Ga-labelled SST analogues PET/CT. This review focuses on the importance of combined imaging with [68Ga]Ga-labelled SST analogues and [18F]FDG for the management of GEP-NENs.

Gastroenteropancreatic neuroendocrine tumors: Role of surgery

Natural history of gastroenteropancreatic (GEP) Neuroendocrine tumors (NETs) is better and better known so indications of surgery are presently selective. Surgical resection, but also endoscopic resection and observation, can be proposed for gastric NETs according to presentation, size and grade. For small bowel NETs, resection is frequently needed but should obtain the best compromise between radicality and postoperative functional disorders. Appendiceal NETs are frequently diagnosed by appendectomy for appendicitis, but some patients at high risk for lymph node metastasis and recurrence should be reoperated for radical resection. Rectal NETs are often diagnosed incidentally; the smallest (<1cm) can be resected endoscopically but the most aggressive need a oncological proctectomy. Pancreatic NETs represent a wide spectrum, ranging from fully benign tumors to very aggressive ones. Insulinomas are mostly benign, responsible for incapacitating symptoms despite medical treatment, and should ideally be treated by parenchyma sparing resection, mainly enucleation. Conversely, symptoms of gastrinomas are efficiently treated medically but their resection needs an oncological approach. Nonfunctioning PNETs are more and more frequently and incidentally discovered. According to their size, presentation and patient's characteristics, they need a resection (oncological or parenchyma-sparing) or a close observation.

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.

Current best practice in the management of neuroendocrine tumors

Neuroendocrine neoplasms are rare tumors that display marked heterogeneity with varying natural history, biological behavior, response to therapy and prognosis. Their management is complex, particularly as a number of them may be associated with a secretory syndrome and involve a variety of options. A number of factors such as proliferation rate, degree of differentiation, functionality and extent of the disease are mostly utilized to tailor treatment accordingly, ideally in the context of a multidisciplinary team. In addition, a number of relevant scientific societies have published therapeutic guidelines in an attempt to direct and promote evidence-based treatment. Surgery remains the treatment of choice with an intention to cure while it may also be recommended in some cases of metastatic disease and difficult to control secretory syndromes. Long-acting somatostatin analogs constitute the main treatment for the majority of functioning tumors, whereas specific evolving agents such as telotristat may be used for the control of carcinoid syndrome and related sequelae. In patients with advanced disease not amenable to surgical resection, treatment options include locoregional therapies, long-acting somatostatin analogs, molecular targeted agents, radionuclides, chemotherapy and recently immunotherapy, alone or in combination. However, the ideal time of treatment initiation, sequence of administration of different therapies and identification of robust prognostic markers to select the most appropriate treatment for each individual patient still need to be defined.

Unmet Needs in Functional and Nonfunctional Pancreatic Neuroendocrine Neoplasms

Recently, the European Neuroendocrine Tumor Society (ENETS) held working sessions composed of members of the advisory board and other neuroendocrine neoplasm (NEN) experts to attempt to identify unmet needs in NENs in different locations or with advanced/poorly differentiated NENs. This report briefly summarizes the main proposed areas of unmet needs in patients with functional and nonfunctional pancreatic NENs.

Imaging of pancreatic neuroendocrine tumors: recent advances, current status, and controversies

Recently, there have been a number of advances in imaging pancreatic neuroendocrine tumors (panNETs), as well as other neuroendocrine tumors (NETs), which have had a profound effect on the management and treatment of these patients, but in some cases are also associated with controversies. Areas covered: These advances are the result of numerous studies attempting to better define the roles of both cross-sectional imaging, endoscopic ultrasound, with or without fine-needle aspiration, and molecular imaging in both sporadic and inherited panNET syndromes; the increased attempt to develop imaging parameters that correlate with tumor classification or have prognostic value; the rapidly increasing use of molecular imaging in these tumors and the attempt to develop imaging parameters that correlate with treatment/outcome results. Each of these areas and the associated controversies are reviewed. Expert commentary: There have been numerous advances in all aspects of the imaging of panNETs, as well as other NETs, in the last few years. The advances are leading to expanded roles of imaging in the management of these patients and the results being seen in panNETs/GI-NETs with these newer techniques are already being used in more common tumors.

Neuroendocrine neoplasms of rectum: A management update

The estimated annual incidence of R-NENs is 1.04 per 100,000 persons although the real incidence may be underestimated, as not all R-NEN are systematically reported in registers. Also the prevalence has increased substantially, reflecting the rising incidence and indolent nature of R-NENs, showing the highest prevalence increase among all site of origin of NENs. The size of the tumor reveals the behavior of R-NENs where the risk for metastatic spread increases for lesions > 10 mm. Applying the WHO 2010 grading system to whole NENs originating in the gastroenteropancreatic system, R-NENs are classified as Well-Differentiated Neuroendocrine Tumors (WD-NET), which contain NET G1 and NET G2, and Poorly-Differentiated Carcinomas (PD-NEC) enclosing only G3 neoplasms for which the term carcinoma is applied. The treatment is endoscopic resection in most cases: conventional polypectomy or endoscopic mucosal resection (EMR) for smaller lesions or endoscopic submucosal resection with a ligation device (ESMR-L), cap-assisted EMR (EMR-C) and endoscopic submucosal dissection (ESD). However it is important to know when the endoscopic treatment is not enough, and surgical treatment is indicated, or when the latter could be unnecessary. For PD-NECs, it has recently been demonstrated that chemoradiotherapy is associated with a similar long-term survival to that obtained with surgery. As well, new targeted-agents chemotherapy may be indicated for metastatic WD-NETs.

Clinical Usefulness of 18F-Fluorodeoxyglucose Positron Emission Tomography in the Diagnostic Algorithm of Advanced Entero-Pancreatic Neuroendocrine Neoplasms

Background

The role of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in the diagnostic algorithm of entero-pancreatic neuroendocrine neoplasms (EP NENs) is unclear because most available data derive from heterogeneous populations in terms of tumor biology and disease status at time of examination. The aim of this study was to determine the ability of 18F-FDG PET to identify patients with more aggressive disease among those with advanced EP NENs.

Subjects, Materials, and Methods . Patients with advanced EP NENs and known disease status (progressive disease [PD] or stable disease [SD]) according to imaging procedures, who received 18F-FDG PET and computed tomography scans during a time frame of 1 month, were included.

Results

A total of 93 patients, including 69 patients with pancreatic NENs and 24 patients with small-intestine NENs, were included. At the time of study entry, 64 patients (68.8%) had PD, and the remaining 29 patients (31.2%) had SD. A total of 62 patients (66.7%) had positive 18F-FDG PET, whereas 18F-FDG PET was negative in the remaining 31 patients (33.3%). Overall, 18F-FDG PET sensitivity and specificity to detect PD were 90.6% and 86.2%, respectively, resulting in a diagnostic accuracy of 89.2%. A positive 18F-FDG PET was significantly associated with PD at the time of study entry (p &lt; .0001 at multivariate analysis). Although a higher proportion of 18F-FDG PET-positive examinations were observed in patients with higher tumor grade (p = .01), 53.8% of patients with grade 1 neuroendocrine tumors (NETs) had positive 18F-FDG PET, and 37.5% of patients with grade 2 NETs had negative 18F-FDG PET. Overall survival was significantly shorter in 18F-FDG PET-positive patients (median: 60 months) in comparison with 18F-FDG PET-negative patients (median not reached; p = .008).

Conclusion

18F-FDG PET has a high diagnostic accuracy to identify progression of disease with unfavorable clinical outcome in patients with advanced EP NENs. Knowledge of disease status and G grading are key factors for physicians to better select patients for whom 18F-FDG PET is clinically useful.

Implications for Practice

The findings of the present study may help physicians dealing with advanced neuroendocrine neoplasms to select patients for whom 18F-fluorodeoxyglucose positron emission tomography is useful to predict poor clinical outcome.

Clinical Usefulness of 18F-Fluorodeoxyglucose Positron Emission Tomography in the Diagnostic Algorithm of Advanced Entero-Pancreatic Neuroendocrine Neoplasms

BACKGROUND

The role of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in the diagnostic algorithm of entero-pancreatic neuroendocrine neoplasms (EP NENs) is unclear because most available data derive from heterogeneous populations in terms of tumor biology and disease status at time of examination. The aim of this study was to determine the ability of 18F-FDG PET to identify patients with more aggressive disease among those with advanced EP NENs. Subjects, Materials, and Methods . Patients with advanced EP NENs and known disease status (progressive disease [PD] or stable disease [SD]) according to imaging procedures, who received 18F-FDG PET and computed tomography scans during a time frame of 1 month, were included.

RESULTS

A total of 93 patients, including 69 patients with pancreatic NENs and 24 patients with small-intestine NENs, were included. At the time of study entry, 64 patients (68.8%) had PD, and the remaining 29 patients (31.2%) had SD. A total of 62 patients (66.7%) had positive 18F-FDG PET, whereas 18F-FDG PET was negative in the remaining 31 patients (33.3%). Overall, 18F-FDG PET sensitivity and specificity to detect PD were 90.6% and 86.2%, respectively, resulting in a diagnostic accuracy of 89.2%. A positive 18F-FDG PET was significantly associated with PD at the time of study entry (p < .0001 at multivariate analysis). Although a higher proportion of 18F-FDG PET-positive examinations were observed in patients with higher tumor grade (p = .01), 53.8% of patients with grade 1 neuroendocrine tumors (NETs) had positive 18F-FDG PET, and 37.5% of patients with grade 2 NETs had negative 18F-FDG PET. Overall survival was significantly shorter in 18F-FDG PET-positive patients (median: 60 months) in comparison with 18F-FDG PET-negative patients (median not reached; p = .008).

CONCLUSION

18F-FDG PET has a high diagnostic accuracy to identify progression of disease with unfavorable clinical outcome in patients with advanced EP NENs. Knowledge of disease status and G grading are key factors for physicians to better select patients for whom 18F-FDG PET is clinically useful.

IMPLICATIONS FOR PRACTICE

The findings of the present study may help physicians dealing with advanced neuroendocrine neoplasms to select patients for whom 18F-fluorodeoxyglucose positron emission tomography is useful to predict poor clinical outcome.

The utility of 68Ga-DOTATATE positron-emission tomography/computed tomography in the diagnosis, management, follow-up and prognosis of neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare neoplasms that emerge mainly from the GI tract, pancreas and respiratory tract. The incidence of NETs has increased more than sixfold in the last decades. NETs typically express somatostatin receptors on their cell surface, which can be targeted by 'cold' somatostatin analogs for therapy or by 'hot' radiolabeled somatostatin analogs for tumor localization and treatment. 68-Gallium-DOTA peptides (DOTATATE, DOTATOC, DOTANOC) positron emission tomography/computed tomography is a highly accurate imaging modality for NETs that has been found to be more sensitive for NET detection than other imaging modalities. In the current review, we will discuss the clinical utility of 68-Gallium-DOTATATE positron emission tomography/computed tomography for the diagnosis and management of patients with NETs.

The future: diagnostic and imaging advances in MEN1 therapeutic approaches and management strategies

Prospective randomized data are lacking, but current clinical expert guidelines recommend annual screening examinations, including laboratory assessments and various imaging modalities (e.g. CT, MRI, scintigraphy and EUS) for patients with multiple endocrine neoplasia type 1 (MEN1). Routine screening is proposed to detect and localize neuroendocrine manifestations as early as possible. The goal is timely intervention to improve quality of life and to increase life expectancy by preventing the development of life-threatening hormonal syndromes and/or metastatic disease. In recent years, some studies compared different and new imaging methods regarding their sensitivity and utility in MEN1 patients. This present article reviews the proposed diagnostic tools for MEN1 screening as well as potential future perspectives.

Utility of FDG-PET Imaging for Risk Stratification of Pancreatic Neuroendocrine Tumors in MEN1

CONTEXT

Patients with multiple endocrine neoplasia type 1 (MEN1) are at high risk of malignant pancreatic neuroendocrine tumors (pNETs). Structural imaging is typically used to screen for pNETs but is suboptimal for stratifying malignant potential.

OBJECTIVE

To determine the utility of fluorodeoxyglucose (18F) positron emission tomography/computed tomography (18F-FDG PET/CT) for predicting the malignant potential of pNETs in MEN1.

DESIGN

Retrospective observational study.

SETTING

Tertiary referral hospital.

PATIENTS

Forty-nine adult patients with MEN1 carrying a common MEN1 mutation who underwent 18F-FDG PET/CT for MEN1 surveillance between 1 January 2010 and 30 September 2016.

INTERVENTIONS

Structural and functional imaging (magnetic resonance imaging, CT, ultrasonography, and 18F-FDG PET/CT) and surgical histopathology.

MAIN OUTCOME MEASURES

pNET size, behavior, and histopathology.

RESULTS

Twenty-five (51.0%) of 49 patients studied had pancreatic lesions on structural imaging. Five (25%) of these had 18F-FDG-PET-avid lesions. In addition, two had solitary FDG-avid liver lesions, and one a pancreatic focus without structural correlate. Eight patients with pNETs underwent surgery (three FDG-avid lesions and five nonavid pNETs). The Ki-67 index was ≥5% in FDG-avid pNETs and <2% in nonavid pNETs. Overall, six of the eight (75%) patients with FDG-avid hepatopancreatic lesions harbored aggressive or metastatic NETs compared with one of 41 patients (2.4%) without hepatopancreatic FDG avidity [P < 0.001; sensitivity; 85.7% (95% confidence interval [CI], 48.7% to 99.3%); specificity, 95.2% (95% CI, 84.2% to 99.2%)].

CONCLUSION

18F-FDG PET/CT is an effective screening modality in MEN1 for identifying pNETs of increased malignant potential. Surgical resection is recommended for FDG-avid pNETs.

MIB-1 Index-Stratified Assessment of Dual-Tracer PET/CT with 68Ga-DOTATATE and 18F-FDG and Multimodality Anatomic Imaging in Metastatic Neuroendocrine Tumors of Unknown Primary in a PRRT Workup Setting

Our aim was to comparatively assess dual-tracer PET/CT (⁶⁸Ga-DOTATATE and ¹⁸F-FDG) and multimodality anatomic imaging in studying metastatic neuroendocrine tumors (NETs) of unknown primary (CUP-NETs) scheduled for peptide receptor radionuclide therapy for divergence of tracer uptake on dual-tracer PET/CT, detection of primary, and overall lesion detection vis-a-vis tumor proliferation index (MIB-1/Ki-67). Methods: Fifty-one patients with CUP-NETs (25 men, 26 women; age, 22-74 y), histopathologically proven and thoroughly investigated with conventional imaging modalities (ultrasonography, CT/contrast-enhanced CT, MRI, and endoscopic ultrasound, wherever applicable), were retrospectively analyzed. Patients were primarily referred for deciding on feasibility of peptide receptor radionuclide therapy (except 2 patients), and all had undergone ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET/CT as part of pretreatment workup. The sites of metastases included liver, lung/mediastinum, skeleton, abdominal nodes, and other soft-tissue sites. Patients were divided into 5 groups on the basis of MIB-1/Ki-67 index on a 5-point scale: group I (1%-5%) (n = 35), group II (6%-10%) (n = 8), group III (11%-15%) (n = 4), group IV (16%-20%) (n = 2), and group V (>20%) (n = 2). Semiquantitative analysis of tracer uptake was undertaken by SUV_max of metastatic lesions and the primary (when detected). The SUV_max values were studied over increasing MIB-1/Ki-67 index. The detection sensitivity of ⁶⁸Ga-DOTATATE for primary and metastatic lesions was assessed and compared with other imaging modalities including ¹⁸F-FDG PET/CT. Results: Unknown primary was detected on ⁶⁸Ga-DOTATATE in 31 of 51 patients, resulting in sensitivity of 60.78% whereas overall lesion detection sensitivity was 96.87%. The overall lesion detection sensitivities (individual groupwise from group I to group V) were 97.75%, 87.5%, 100%, 100%, and 66.67%, respectively. As MIB-1/Ki-67 index increased, ⁶⁸Ga-DOTATATE uptake decreased in metastatic and primary lesions (mean SUV_max, 43.5 and 22.68 g/dL in group I to 22.54 and 16.83 g/dL in group V, respectively), whereas ¹⁸F-FDG uptake showed a gradual rise (mean SUV_max, 3.66 and 2.86 g/dL in group I to 7.53 and 9.58 g/dL in group V, respectively). There was a corresponding decrease in the ⁶⁸Ga-DOTATATE-to-¹⁸F-FDG uptake ratio with increasing MIB-1/Ki-67 index (from 11.89 in group I to 2.99 in group V). Conclusion: In CUP-NETs, the pattern of uptake on dual-tracer PET (⁶⁸Ga-DOTATATE and ¹⁸F-FDG) correlates well with tumor proliferation index with a few outliers; combined dual-tracer PET/CT with MIB-1/Ki-67 index would aid in better whole-body assessment of tumor biology in CUP-NETs.

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.

Management of neuroendocrine carcinomas of the pancreas (WHO G3): A tailored approach between proliferation and morphology

Neuroendocrine carcinomas (NEC) of the pancreas are defined by a mitotic count > 20 mitoses/10 high power fields and/or Ki67 index > 20%, and included all the tumors previously classified as poorly differentiated endocrine carcinomas. These latter are aggressive malignancies with a high propensity for distant metastases and poor prognosis, and they can be further divided into small- and large-cell subtypes. However in the NEC category are included also neuroendocrine tumors with a well differentiated morphology but ki67 index > 20%. This category is associated with better prognosis and does not significantly respond to cisplatin-based chemotherapy, which represents the gold standard therapeutic approach for poorly differentiated NEC. In this review, the differences between well differentiated and poorly differentiated NEC are discussed considering both pathology, imaging features, treatment and prognostic implications. Diagnostic and therapeutic flowcharts are proposed. The need for a revision of current classification system is stressed being well differentiated NEC a more indolent disease compared to poorly differentiated tumors.

Digestive neuroendocrine neoplasms: A 2016 overview

Digestive neuroendocrine neoplasms (DNENs) have an incidence of 2.39 per 100,000 inhabitants per year, and a prevalence of 35 cases per 100,000; the gap between these rates is to be referred to the relatively long survival that characterizes the majority of these tumors, which can be thus considered as chronic oncological diseases. Up to 80% of patients are stage IV since the first diagnosis, presenting a 5-yr overall survival rate of 35%-55% and a twice higher mortality than limited disease. DNENs express somatostatin receptors in more than 80% of cases, detected through immunohistochemistry or functional imaging tests (FITs). This feature identifies patients who may benefit from "cold" somatostatin analogs (SSAs) or peptide receptors radionuclide therapy, although SSAs are sometimes used also with a negative uptake at FITs. The therapeutic options have been recently increased after the identification of molecular pathways involved in DNENs pathogenesis, and the subsequent use of targeted therapies (i.e., Everolimus and Sunitinib) for these neoplasms. This review offers an overview about pancreatic and small bowel NENs, critically underlining the issues that still need to be clarified and the future perspectives to be investigated.

Gastro-entero-pancreatic neuroendocrine tumors: Is now time for a new approach?

Gastro-entero-pancreatic tumors (GEP-NETs) are rare neoplasms often characterized by an overexpression of somatostatin receptors. Thus, radiolabeled somatostatin analogues have showed an increasing relevance both in diagnosis and treatment, especially in low- and intermediate-differentiated GEP-NETs. These evidences have led to a growing development of new functional imaging techniques as 68Ga-DOTATATE positron emission tomography/computed tomography (PET/CT) proved useful in the management of these neoplasms. However these tumors have a heterogeneous behavior also modifying their aggressiveness through time. Therefore sometimes 18F-fluorodeoxyglucose PET/CT appears to be more appropriate to obtain a better assessment of the disease. According to these considerations, the combination of different functional imaging techniques should be considered in the management of GEP-NETs patients allowing clinicians to choose the tailored therapeutic approach among available options.