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

National practice patterns in the use of endoscopic ultrasound biopsy for resectable Pancreatic Neuroendocrine Tumors: Insights into the role of DOTATATE PET/CT in diagnosis

INTRODUCTION

Pancreatic neuroendocrine tumors (PNETs) are typically diagnosed using endoscopic ultrasound-guided (EUS) biopsy, which can be associated with complications. Since 2016, DOTATATE PET/CT has emerged as an effective tool to localize and stage PNETs.

METHODS

Patients with PNETs who underwent R0 resections were identified from the 2004-2019 National Cancer Database PUF. Joinpoint regression and multivariable logistic regression were used to analyze trends in the use of biopsy.

RESULTS

Of 16,746 R0 resected PNET patients, 44 ​% underwent diagnostic biopsy. Joinpoint regression showed a significant increase in the use of biopsy from 2004 to 2019 (APC 1.80, p ​< ​0.001). A higher percentage of patients diagnosed after DOTATATE approval underwent biopsy compared to those diagnosed before (48 ​% vs. 42 ​%, p ​< ​0.001). Adjusted analysis showed diagnosis after 2016 was associated with increased odds of biopsy (OR ​= ​1.67, p ​< ​0.001).

CONCLUSIONS

Despite technologic advancement with DOTATATE PET/CT, there has been a significant increase in the proportion of resectable PNETs undergoing preoperative biopsy.

Characteristics, therapy, and outcome of rare functioning pancreatic neuroendocrine neoplasms

Functioning pancreatic neuroendocrine neoplasms other than insulinomas and gastrinomas (rf-pNENs) are exceptionally rare tumours. Thus, their characteristics and long-term prognosis have not been well defined. This article aims to present data and experience from a single institution concerning this topic. Twelve of 216 (5.5%) patients with pNENs operated between 2002 and 2022 in the ENETS Centre of Excellence Marburg had rf-pNENs and their data were retrospectively analysed. We identified three vasoactive intestinal polypeptide producing pNENs, four glucagonomas and five calcitoninomas. The tumour could be visualised by preoperative imaging in all 12 patients, and six patients had distant metastases at the time of diagnosis. The tumour was located in the pancreatic tail in nine patients and the median tumour size was 82 (range 12-220) mm. Eleven patients underwent tumour resections (two robotic, nine conventional), nine of which were R0. After a median follow-up of 75 (range 1-247) months, six patients were alive, five of whom had no evidence of disease. All patients who remained disease-free had an initial R0 resection of the primary tumour and no initial liver involvement. This study sheds light on the distinct characteristics and outcomes of these exceedingly rare tumours, offering insights for improved understanding and management.

Stereotactic Body Radiation Therapy for Symptomatic Pancreatic Insulinoma: Two-Case Report and Literature Review

Insulinoma is the most common functional neuroendocrine tumor of the pancreas, with the main clinical symptom being hypoglycemia. The standard treatment is surgery, but some patients are not eligible for surgery, while in those operated on, the risk of perioperative complications is up to 30%. Diazoxide treatment to prevent hypoglycemia is effective only in 50% of patients. To prevent tumor growth and hormonal excess, stereotactic radiotherapy may be an alternative to surgical treatment. In our paper, we present two cases of patients with insulinoma treated successfully with stereotactic body radiation therapy (SBRT).

[Imaging of pancreatic neuroendocrine tumors]

BACKGROUND

Neuroendocrine tumors of the pancreas have a broad biological spectrum. The treatment decision is based on an optimal diagnosis with regard to the local findings and possible locoregional and distant metastases. In addition to purely morphologic imaging procedures, functional parameters are playing an increasingly important role in imaging.

OBJECTIVES

Prerequisites for optimal imaging of the pancreas, technical principles are provided, and the advantages and disadvantages of common cross-sectional imaging techniques as well as clinical indications for these special imaging methods are discussed.

MATERIALS AND METHODS

Guidelines, basic and review papers will be analyzed.

RESULTS

Neuroendocrine tumors of the pancreas have a broad imaging spectrum. Therefore, there is a need for multimodality imaging in which morphologic and functional techniques support each other. While positron emission tomography/computed tomography (PET/CT) can determine the presence of one or more lesions and its/their functional status of the tumor, magnetic resonance imaging (MRI) efficiently identifies the location, relationship to the main duct and the presence of liver metastases. CT allows a better vascular evaluation, even in the presence of anatomical variants as well as sensitive detection of lung metastases.

CONCLUSIONS

Knowledge of the optimal combination of imaging modalities including clinical and histopathologic results and dedicated imaging techniques is essential to achieve an accurate diagnosis to optimize treatment decision-making and to assess therapy response.

Liver Imaging in Gastroenteropancreatic Neuroendocrine Neoplasms

ABSTRACT

The incidence of neuroendocrine neoplasms (NENs) has gradually increased over the past few decades with the majority of patients presenting with metastases on initial presentation. The liver is the most common site of initial metastatic disease, and the presence of liver metastasis is an independent prognostic factor associated with a negative outcome. Because NENs are heterogenous neoplasms with variable differentiation, grading, and risk of grade transformation over time, accurate diagnosis and management of neuroendocrine liver lesions are both important and challenging. This is particularly so with the multiple liver-directed treatment options available. In this review article, we discuss the diagnosis, treatment, and response evaluation of NEN liver metastases.

Increased [68Ga]Ga-SST uptake in the uncinate pancreatic process in new digital PET/CT machine and potential association with clinical and histologic factors in NET patients

INTRODUCTION

A physiological increase in the uptake of [68Ga]Ga-labeled somatostatin analogues ([68Ga]Ga-SST) PET tracers has been reported in the uncinate pancreatic process (UP) and might be even higher in latest generation of PET/CT scanners and might be falsely interpreted as NET. We aimed to investigate the uptake of UP in a large population of NET patients who underwent [68Ga]Ga-SST PET/CT with digital SiPM detectors. We also explored potential associations between UP uptake and various clinical, imaging, and pathological factors routinely assessed in NET patients.

METHODS

We analyzed all consecutive NET patients from July 2018 to June 2022 in this retrospective, single-center study. All patients underwent a [68Ga]Ga-SST PET/CT scan on a digital SiPM PET/CT scanner. On visual analysis, we distinguished between normal linear and homogenous UP uptake or abnormal if otherwise. We compared SUVmax/mean in patients with normal UP uptake to those with abnormal UP uptake with suspicious NET lesions on contrast-enhanced CT (ce-CT) and according to the site of the primary NET (pancreatic NET vs. other), patient gender (female vs. male) and tumor grade (grade 1-2 vs. 3) using a Mann-Whitney test. We also assessed the correlation between SUVmax/mean values in UP with patients' age, primary NET Ki-67 counting, and its SUVmax/mean, TLA and MTV values.

RESULTS

We included 131 NET patients with a total of 34 [68Ga]Ga-DOTATATE PET/CT and 113 [68Ga]Ga-DOTATOC PET/CT scans. An abnormal UP uptake was seen in 32 patients with 65.7% of suspicious NET lesion or extrinsic compression on morphological imaging. Normal UP uptake SUVmax/mean were measured in 115 [68Ga]Ga-SST scans (78.2%) with normal UP uptake and without suspicious lesion on morphological imaging. We found an average SUVmax of 12.3 ± 4.1 for [68Ga]Ga-DOTATATE and 19.8 ± 9.8 g/ml for [68Ga]Ga-DOTATOC, hence higher than those reported in the literature [SUVmax 5 ± 1.6 to 12.6 ± 2.2 g/ml] with significant difference with abnormal UP uptake and between both PET tracers (both p < 0.01). Significant results were a higher UP uptake on [68Ga]Ga-DOTATOC in male patients (p = 0.02) and significant associations between UP uptake on [68Ga]Ga-DOTATOC and SUVmax/mean of the primary tumor (ρ [0.337-0.363]; p [0.01-0.02]).

CONCLUSION

We confirmed a higher and very frequent UP uptake in latest SiPM-detector [68Ga]Ga-SST PET/CT with an even higher uptake in patients that had [68Ga]Ga-DOTATOC PET/CT. SUVmean/max were significantly higher in abnormal UP uptake but there were overlaps with UP SUV values for both [68Ga]Ga-SST and a correlation to morphological imaging is crucial. Besides, significant associations between UP uptake and SUVmean/max of the primary NET as well as patients' gender were seen in the larger cohort of [68Ga]Ga-DOTATOC patients suggesting that both physiological and pathological parameters could affect UP uptake.

Recent developments in the diagnosis of pancreatic neuroendocrine neoplasms

INTRODUCTION

Pancreatic Neuroendocrine Neoplasms (PanNENs) are characterized by a highly heterogeneous clinical and biological behavior, making their diagnosis challenging. PanNENs diagnostic work-up mainly relies on biochemical markers, pathological examination, and imaging evaluation. The latter includes radiological imaging (i.e. computed tomography [CT] and magnetic resonance imaging [MRI]), functional imaging (i.e. 68Gallium [68 Ga]Ga-DOTA-peptide PET/CT and Fluorine-18 fluorodeoxyglucose [18F]FDG PET/CT), and endoscopic ultrasound (EUS) with its associated procedures.

AREAS COVERED

This review provides a comprehensive assessment of the recent advancements in the PanNENs diagnostic field. PubMed and Embase databases were used for the research, performed from inception to October 2023.

EXPERT OPINION

A deeper understanding of PanNENs biology, recent technological improvements in imaging modalities, as well as progresses achieved in molecular and cytological assays, are fundamental players for the achievement of early diagnosis and enhanced preoperative characterization of PanNENs. A multimodal diagnostic approach is required for a thorough disease assessment.

Preoperative prediction of pancreatic neuroendocrine tumor grade based on 68Ga-DOTATATE PET/CT

OBJECTIVE

To establish a prediction model for preoperatively predicting grade 1 and grade 2/3 tumors in patients with pancreatic neuroendocrine tumors (PNETs) based on 68Ga-DOTATATE PET/CT.

METHODS

Clinical data of 41 patients with PNETs were included in this study. According to the pathological results, they were divided into grade 1 and grade 2/3. 68Ga-DOTATATE PET/CT images were collected within one month before surgery. The clinical risk factors and significant radiological features were filtered, and a clinical predictive model based on these clinical and radiological features was established. 3D slicer was used to extracted 107 radiomic features from the region of interest (ROI) of 68Ga-dotata PET/CT images. The Pearson correlation coefficient (PCC), recursive feature elimination (REF) based five-fold cross validation were adopted for the radiomic feature selection, and a radiomic score was computed subsequently. The comprehensive model combining the clinical risk factors and the rad-score was established as well as the nomogram. The performance of above clinical model and comprehensive model were evaluated and compared.

RESULTS

Adjacent organ invasion, N staging, and M staging were the risk factors for PNET grading (p < 0.05). 12 optimal radiomic features (3 PET radiomic features, 9 CT radiomic features) were screen out. The clinical predictive model achieved an area under the curve (AUC) of 0.785. The comprehensive model has better predictive performance (AUC = 0.953).

CONCLUSION

We proposed a comprehensive nomogram model based on 68Ga-DOTATATE PET/CT to predict grade 1 and grade 2/3 of PNETs and assist personalized clinical diagnosis and treatment plans for patients with PNETs.

Diagnosis, Management and Theragnostic Approach of Gastro-Entero-Pancreatic Neuroendocrine Neoplasms

Gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs) constitute an ideal target for radiolabeled somatostatin analogs. The theragnostic approach is able to combine diagnosis and therapy by the identification of a molecular target that can be diagnosed and treated with the same radiolabeled compound. During the last years, advances in functional imaging with the introduction of somatostatin analogs and peptide receptor radionuclide therapy, have improved the diagnosis and treatment of GEP-NENs. Moreover, PET/CT imaging with ¹⁸F-FDG represents a complementary tool for prognostic evaluation of patients with GEP-NENs. In the field of personalized medicine, the theragnostic approach has emerged as a promising tool in diagnosis and management of patients with GEP-NENs. The aim of this review is to summarize the current evidence on diagnosis and management of patients with GEP-NENs, focusing on the theragnostic approach.

Case Report: Giant insulinoma, a very rare tumor causing hypoglycemia

Insulinomas, with an incidence of 4 cases per million individuals per year, remain amongst the most frequent functional neuroendocrine tumors. The usual diameter of insulinomas usually remains under 3 cm of major axis. However, 44 exceptional cases of "giant insulinomas", have been reported worldwide, generally exceeding 9 cm in major axis. In this article, we report the case of a 38-year-old woman whom suffered from chronic hypoglycemia despite treatment with diazoxide. Abdominal CT-scan revealed a 88 x 73 mm mass located at the tail of the pancreas. Following surgical excision, histopathological analysis confirmed G1 neuroendocrine tumor, with focal cytoplasmic expression of insulin in tumor cells. After a 16-month follow-up period, the patient didn't address any specific complaint, and no disease recurrence and/or metastasis were observed. A ⁶⁸Ga-DOTATATE-PET scan was performed 6 months after surgery, which came back normal. Genetic evaluation has not been performed in our patient. The physiopathology of giant insulinomas remain unexplained, however with possible relationship with type 1 multiple endocrine neoplasia, sporadic somatic YY1 mutations and possible transformation of bulky non-functional pancreatic neuroendocrine tumors to a functional phenotype, with slow insulin secretion. While giant insulinomas remain rare in the literature, multicentric genetic analysis of tumor samples might reveal unique features of this rare subtype of neuroendocrine pancreatic tumors. Insulinomas of large size tend to have greater malignancy and higher rates of invasiveness. Careful follow-up, especially for liver and lymph node metastases, must be performed using functional imaging techniques to avoid disease relapse.

Peptide Radioligands in Cancer Theranostics: Agonists and Antagonists

The clinical success of radiolabeled somatostatin analogs in the diagnosis and therapy-"theranostics"-of tumors expressing the somatostatin subtype 2 receptor (SST₂R) has paved the way for the development of a broader panel of peptide radioligands targeting different human tumors. This approach relies on the overexpression of other receptor-targets in different cancer types. In recent years, a shift in paradigm from internalizing agonists to antagonists has occurred. Thus, SST₂R-antagonist radioligands were first shown to accumulate more efficiently in tumor lesions and clear faster from the background in animal models and patients. The switch to receptor antagonists was soon adopted in the field of radiolabeled bombesin (BBN). Unlike the stable cyclic octapeptides used in the case of somatostatin, BBN-like peptides are linear, fast to biodegradable and elicit adverse effects in the body. Thus, the advent of BBN-like antagonists provided an elegant way to obtain effective and safe radiotheranostics. Likewise, the pursuit of gastrin and exendin antagonist-based radioligands is advancing with exciting new outcomes on the horizon. In the present review, we discuss these developments with a focus on clinical results, commenting on challenges and opportunities for personalized treatment of cancer patients by means of state-of-the-art antagonist-based radiopharmaceuticals.

Advancements of molecular imaging and radiomics in pancreatic carcinoma

Despite the recent progress of medical technology in the diagnosis and treatment of tumors, pancreatic carcinoma remains one of the most malignant tumors, with extremely poor prognosis partly due to the difficulty in early and accurate imaging evaluation. This paper focuses on the research progress of magnetic resonance imaging, nuclear medicine molecular imaging and radiomics in the diagnosis of pancreatic carcinoma. We also briefly described the achievements of our team in this field, to facilitate future research and explore new technologies to optimize diagnosis of pancreatic carcinoma.

Diagnostic Management of Gastroenteropancreatic Neuroendocrine Neoplasms: Technique Optimization and Tips and Tricks for Radiologists

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) comprise a heterogeneous group of neoplasms, which derive from cells of the diffuse neuroendocrine system that specializes in producing hormones and neuropeptides and arise in most cases sporadically and, to a lesser extent, in the context of complex genetic syndromes. Furthermore, they are primarily nonfunctioning, while, in the case of insulinomas, gastrinomas, glucagonomas, vipomas, and somatostatinomas, they produce hormones responsible for clinical syndromes. The GEP-NEN tumor grade and cell differentiation may result in different clinical behaviors and prognoses, with grade one (G1) and grade two (G2) neuroendocrine tumors showing a more favorable outcome than grade three (G3) NET and neuroendocrine carcinoma. Two critical issues should be considered in the NEN diagnostic workup: first, the need to identify the presence of the tumor, and, second, to define the primary site and evaluate regional and distant metastases. Indeed, the primary site, stage, grade, and function are prognostic factors that the radiologist should evaluate to guide prognosis and management. The correct diagnostic management of the patient includes a combination of morphological and functional evaluations. Concerning morphological evaluations, according to the consensus guidelines of the European Neuroendocrine Tumor Society (ENETS), computed tomography (CT) with a contrast medium is recommended. Contrast-enhanced magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI), is usually indicated for use to evaluate the liver, pancreas, brain, and bones. Ultrasonography (US) is often helpful in the initial diagnosis of liver metastases, and contrast-enhanced ultrasound (CEUS) can solve problems in characterizing the liver, as this tool can guide the biopsy of liver lesions. In addition, intraoperative ultrasound is an effective tool during surgical procedures. Positron emission tomography (PET-CT) with FDG for nonfunctioning lesions and somatostatin analogs for functional lesions are very useful for identifying and evaluating metabolic receptors. The detection of heterogeneity in somatostatin receptor (SSTR) expression is also crucial for treatment decision making. In this narrative review, we have described the role of morphological and functional imaging tools in the assessment of GEP-NENs according to current major guidelines.

Management of Small Nonfunctioning Pancreatic Neuroendocrine Neoplasms: Current Opinion and Controversies

The incidence of small and asymptomatic pancreatic neuroendocrine neoplasms (PNENs) has increased due to the widespread use of high-resolution diagnostic imaging in screening programs. Most PNENs are slow-growing indolent neoplasms. However, a local invasion or metastasis can sometimes occur with PNENs, leading to a poor prognosis. The management of small, nonfunctioning PNENs remains under debate. The National Comprehensive Cancer Network guidelines recommend observation in selected cases of small PNENs less than 2 cm. Pancreatic surgery remains a high-risk operation with a 28-30% morbidity and 1% mortality. Therefore, the decision on how to manage small PNENs is challenging. This review focuses on the management of small nonfunctioning PNENs. We also highlight the malignant potential of small PNENs according to tumor size, tumor grade, and tumor biomarker. Endoscopic-ultrasound-guided biopsy is recommended to evaluate the potential risk of malignancy. Furthermore, we discuss the current guidelines and future directions for the management of small PNENs.

Position Statement on the Diagnosis, Treatment, and Response Evaluation to Systemic Therapies of Advanced Neuroendocrine Tumors, With a Special Focus on Radioligand Therapy

BACKGROUND

The aim of this study was to provide a guidance for the management of neuroendocrine tumors (NETs) in clinical practice.

MATERIAL AND METHODS

Nominal group and Delphi techniques were used. A steering committee of 8 experts reviewed the current management of NETs, identified controversies and gaps, critically analyzed the available evidence, and formulated several guiding statements for clinicians. Subsequently, a panel of 26 experts, was selected to test agreement with the statements through 2 Delphi rounds. Items were scored on a 4-point Likert scale from 1 = totally agree to 4 = totally disagree. The agreement was considered if ≥75% of answers pertained to Categories 1 and 2 (consensus with the agreement) or Categories 3 and 4 (consensus with the disagreement).

RESULTS

Overall, 132 statements were proposed, which incorporated the following areas: (1) overarching principles; (2) progression and treatment response criteria; (3) advanced gastro-enteric NETs; (4) advanced pancreatic NETs; (5) advanced NETs in other locations; (6) re-treatment with radioligand therapy (RLT); (7) neoadjuvant therapy. After 2 Delphi rounds, only 4 statements lacked a clear consensus. RLT was not only recommended in the sequencing of different NETs but also as neoadjuvant treatment, while several indications for retreatment with RLT were also established.

CONCLUSION

This document sought to pull together the experts' attitudes when dealing with different clinical scenarios of patients suffering from NETs, with RLT having a specific role where evidence-based data are limited.

The utility of 18F-FDG PET/CT in the diagnosis, staging of non-functioning pancreatic neuroendocrine tumors

Background

The non-functional PNETs are often discovered incidentally, they are commonly malignant and commonly present at a late stage with large size. We evaluate in this study the usefulness of 18F-FDG PET/CT in the detection and staging of non-functioning PNETs.

Results

Thirty patients with non-functioning PNETs were involved in this prospective study over a period starting from September 2016 to March 2021. Age ranged from 33 to 79 years. 18F-FDG PET/CT detected 26 patients had SUV max ≥ 2.5 of primary lesions and 4 lesions had SUV max < 2.5. There was no statistical significant between the site of the lesions and the type of grading of the tumors. 32 distant metastatic lesions were detected which show SUVmax ≥ 2.5 and only 9%where below 2.5. Of 30 patients, 4 patients (13.3%) of well differentiated tumor had altered their clinical strategies according to the results of PET/CT examinations. 18F-FDG PET/CT upstaged 1 patient with stage IB and 3 patients with IIA and B to stage IV.

Conclusion

The increased use of 18F-FDG PET/CT in the investigation of patient with PNETs allows for more accurate staging and therefore more appropriate management decision.

Peptide receptor radionuclide therapy as a tool for the treatment of severe hypoglycemia in patients with primary inoperable insulinoma

Objectives

Severe hypoglycemia in a course of inoperable insulinoma may be life-threating and often it is not well controlled, even by high doses of diazoxide requiring second line treatment. Among available methods PRRT is characterized by relatively low toxicity and is connected with favorable antitumor effect. The aim of the study was an evaluation of the PRRT effectiveness in control of hypoglycemia in patients with primary inoperable insulinoma.

Methods

Three patients (female with metastatic insulinoma, male with primary inoperable pancreatic tumor, female with MEN1 syndrome and hepatic metastases) were treated with PRRT due to severe hypoglycemia poorly controlled by diazoxide in course of primary inoperable insulinoma.

Results

Patient 1 baseline fasting glucose concentration increased from 2.4 mmol/L [3.30–5.60] to 5.9 mmol/L after PRRT. In patient 2 fasting glucose level 2.30 mmol/L increased after PRRT to 7.0 mmol/L, while baseline insulin level initially 31.15 uU/mL [2.6–24.9] decreased to 15.4 uU/mL. In patients 3, baseline fasting glucose level 2.5 mmol/L increased after PRRT to 7.9 mmol/L, and insulin decreased from 57.9 uU/mL to 6.3 uU/mL. In imaging there was partial response (PR) in patient 1 and 2 and stabilization of the tumor size in patient 3. In patient 2 reduction of tumor infiltration let for curative surgery performed 4 months after PPRT.

Conclusions

PRRT may be effective as a first or second line treatment in management of hypoglycemia for patients with hormonally active inoperable insulinoma.

Current update on imaging for pancreatic neuroendocrine neoplasms

Pancreatic neuroendocrine neoplasms (panNEN) are a heterogeneous group of tumors with differing pathological, genetic, and clinical features. Based on clinical findings, they may be categorized into functioning and nonfunctioning tumors. Adoption of the 2017 World Health Organization classification system, particularly its differentiation between grade 3, well-differentiated pancreatic neuroendocrine tumors (panNET) and grade 3, poorly-differentiated pancreatic neuroendocrine carcinomas (panNEC) has emphasized the role imaging plays in characterizing these lesions. Endoscopic ultrasound can help obtain biopsy specimen and assess tumor margins and local spread. Enhancement patterns on computed tomography (CT) and magnetic resonance imaging (MRI) may be used to classify panNEN. Contrast enhanced MRI and diffusion-weighted imaging have been reported to be useful for characterization of panNEN and quantifying metastatic burden. Current and emerging radiotracers have broadened the utility of functional imaging in evaluating panNEN. Fluorine-18 fluorodeoxyglucose positron emission tomography (PET)/CT and somatostatin receptor imaging such as Gallium-68 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid–octreotate PET/CT may be useful for improved identification of panNEN in comparison to anatomic modalities. These new techniques can also play a direct role in optimizing the selection of treatment for individuals and predicting tumor response based on somatostatin receptor expression. In addition, emerging methods of radiomics such as texture analysis may be a potential tool for staging and outcome prediction in panNEN, however further investigation is required before clinical implementation.

The new WHO classification of gastrointestinal neuroendocrine tumors and immunohistochemical expression of somatostatin receptor 2 and 5

The 2019 World Health Organization (WHO) classification of gastrointestinal tumors defines well-differentiated grade 3 neuroendocrine tumors, the mixed neuroendocrine-non-neuroendocrine tumors (MiNENs) and classifies goblet cell carcinoid as goblet cell adenocarcinoma. The expression of somatostatin receptors (SSTRs) is the foundation for somatostatin analogue therapy. At present, there are only a few studies that have analyzed the immunohistochemical reactivity of SSTRs in gastrointestinal neuroendocrine neoplasms (NENs). The aim of the present study was to evaluate the immunohistochemical expression of SSTR2 and SSTR5 in gastrointestinal NENs and goblet cell adenocarcinomas and the correlation of these markers with clinical and morphological factors. The study included 67 patients with NENs and 4 patients with adenocarcinoma ex-goblet cell carcinoid diagnosed between January 2008 and December 2018. Tumors were reclassified according to the 2019 WHO classification. Immunohistochemical staining for chromogranin A, synaptophysin, Ki-67, p53, SSTR2, and SSTR5 were performed in all the cases. The results showed that, G1 and G2 neuroendocrine tumors were more common SSTR2-positive in comparison with G3 carcinomas (P<0.0001). In addition, 33.3% of neuroendocrine carcinomas and 2 cases of low-grade adenocarcinoma ex-goblet cell carcinoid were SSTR2-positive. Neuroendocrine carcinomas had significantly lower SSTR2 and SSTR5 expression compared with well-differentiated neuroendocrine tumors (P=0.0130; P=0.0437, respectively). The SSTR2 expression in the early tumor stages was 100%, more often than in advanced stages (55.6%; P=0.0011). The results demonstrated the decrease in SSTR2 expression with increasing malignancy and tumor stage. The SSTR2-positive expression in neuroendocrine carcinomas and adenocarcinoma ex-goblet cell carcinoid provides evidence for the benefits of somatostatin analog treatment associated with surgery and chemotherapy.

Imaging of neuroendocrine tumors: A pictorial review of the clinical value of different imaging modalities

Neuroendocrine tumors (NETs) are multifaceted tumors occurring in a variety of organs and often present as metastatic at the time of diagnosis. Accurate staging is the most significant factor in therapy planning, but it remains a challenge. Imaging is established as the cornerstone for disease detection/diagnosis, staging, and follow up. To accurately assess and monitor tumor burden in patients with NETs, various imaging techniques have been developed and optimized. Current recommendations for the imaging of patients with NETs include a combination of both morphologic (or anatomic) and molecular imaging, but a final choice can be puzzling for clinicians. Recognizing that there is no uniform sequence consensus on the "best" imaging test, and the heterogeneity of technologic availability at different centers, we hope to provide a pictorial review of the different imaging techniques and their role and utility in management of patients with NETs, aimed to provide a practical guide for all clinicians.