Biochemical Diagnosis and Preoperative Imaging of Gastroenteropancreatic Neuroendocrine Tumors

Small Bowel Neuroendocrine Neoplasms-A Review

ABSTRACT

Neuroendocrine neoplasms (NENs) are rapidly evolving small bowel tumors, and the patients are asymptomatic at the initial stages. Metastases are commonly observed at the time of presentation and diagnosis. This review addresses the small bowel NEN (SB-NEN) and its molecular, histological, and imaging features, which aid diagnosis and therapy guidance. Somatic cell number alterations and epigenetic mutations are studied to be responsible for sporadic and familial SB-NEN. The review also describes the grading of SB-NEN in addition to rare histological findings such as mixed neuroendocrine-non-NENs. Anatomic and nuclear imaging with conventional computed tomography, magnetic resonance imaging, computed tomographic enterography, and positron emission tomography are adopted in clinical practice for diagnosing, staging, and follow-up of NEN. Along with the characteristic imaging features of SB-NEN, the therapeutic aspects of imaging, such as peptide receptor radionuclide therapy, are discussed in this review.

Neuroendocrine Tumors: Diagnostics

Neuroendocrine neoplasms (NEN) are rare tumors arising from neuroendocrine cells. NEN are ideally suited for a theragnostic approach due to their specific expression of somatostatin receptors (SSTR). SSTR imaging of NEN dates back to the 1980s, but has evolved recently due to the introduction of more sensitive SSTR PET radiotracers. SSTR PET is a primary imaging modality for identifying NEN and characterizing SSTR expression. SSTR PET is complementary to anatomic imaging for assessing tumor response to treatment. SSTR PET is mandated to determine eligibility for peptide receptor radionuclide therapy. Here, the role of imaging to aid management of NEN is reviewed.

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.

Gastric neuroendocrine neoplasms: a primer for radiologists

Gastric neuroendocrine neoplasms are uncommon tumors with variable differentiation and malignant potential. Three main subtypes are recognized: type 1, related to autoimmune atrophic gastritis; type 2, associated with Zollinger-Ellison and MEN1 syndrome; and type 3, sporadic. Although endoscopy alone is often sufficient for diagnosis and management of small, indolent, multifocal type 1 tumors, imaging is essential for evaluation of larger, high-grade, and type 2 and 3 neoplasms. Hypervascular intraluminal gastric masses are typically seen on CT/MRI, with associated perigastric lymphadenopathy and liver metastases in advanced cases. Somatostatin receptor nuclear imaging (such as Ga-68-DOTATATE PET/CT) may also be used for staging and assessing candidacy for peptide receptor radionuclide therapy. Radiotracer uptake is more likely in well-differentiated, lower-grade tumors, and less likely in poorly differentiated tumors, for which F-18-FDG-PET/CT may have additional value. Understanding disease pathophysiology and evolving histologic classifications is particularly useful for radiologists, as these influence tumor behavior, preferred imaging, therapy options, and patient prognosis.

Progress in the Management of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNETs) are a heterogeneous and orphan group of neoplasms that vary in their histology, clinical features, prognosis, and management. The treatment of PNETs is highly dependent on the stage at presentation, tumor grade and differentiation, presence of symptoms from hormonal overproduction or from local growth, tumor burden, and rate of progression. The US Food and Drug Administration has recently approved many novel treatments, which have altered decision making and positively impacted the care and prognosis of these patients. In this review, we focus on the significant progress made in the management of PNETs over the past decade, as well as the active areas of research. Expected final online publication date for the Annual Review of Medicine, Volume 73 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Somatostatin Receptor Imaging and Theranostics: Current Practice and Future Prospects

A new era of precision diagnostics and therapy for patients with neuroendocrine neoplasms began with the approval of somatostatin receptor (SSTR) radiopharmaceuticals for PET imaging followed by peptide receptor radionuclide therapy (PRRT). With the transition from SSTR-based γ-scintigraphy to PET, the higher sensitivity of the latter raised questions regarding the direct application of the planar scintigraphy-based Krenning score for PRRT eligibility. Also, to date, the role of SSTR PET in response assessment and predicting outcome remains under evaluation. In this comprehensive review article, we discuss the current role of SSTR PET in all aspects of neuroendocrine neoplasms, including its relation to conventional imaging, selection of patients for PRRT, and the current understanding of SSTR PET-based response assessment. We also provide a standardized reporting template for SSTR PET with a brief discussion.

Radiological Imaging of Gastro-Entero-Pancreatic Neuroendocrine Tumors. The Review of Current Literature Emphasizing the Diagnostic Value of Chosen Imaging Methods

Despite development of radiologic imaging, detection and follow-up of neuroendocrine neoplasms (NENs) still pose a diagnostic challenge, due to the heterogeneity of NEN, their relatively long-term growth, and small size of primary tumor. A set of information obtained by using different radiological imaging tools simplifies a choice of the most appropriate treatment method. Moreover, radiological imaging plays an important role in the assessment of metastatic lesions, especially in the liver, as well as, tumor response to treatment. This article reviews the current, broadly in use imaging modalities which are applied to the diagnosis of GEP-NETs, (the most common type of NENs) and put emphasis on the strengths and limitations of each modality.

VIPoma: a rare cause of diarrhea. A case report

Introduction: Vasoactive intestinal peptide-secreting tumor (VIPoma) is a rare functional pancreatic neuroendocrine tumor (F-PNET) characterized by secretory diarrhea, hypokalemia, and hypochlorhydria. Its low incidence and high risk of malignancy pose a clinical challenge that requires a high degree of clinical suspicion. Case presentation: A 61-year-old woman visited the emergency department of a tertiary care hospital in Medellín, Colombia, due to chronic diarrhea (7 months) that led to dehydration, renal failure, metabolic acidosis, and hypokalemia. As a result, a treatment based on loperamide, intravenous fluids and broad-spectrum antibiotics was started. In addition, chromogranin A levels of 477 ug/L (<100) were reported, while an abdominal MRI showed a 33x30mm mass in the head and uncinate process of the pancreas, so outpatient surgical management was decided. However, three days after discharge, and due to the persistence of clinical signs, the patient was admitted to another hospital (also a tertiary care hospital), where, given the high suspicion of VIPoma, and once the diarrhea was solved, the mass was removed (Whipple procedure) without any complication. Finally, the diagnosis was confirmed based on serum vasoactive intestinal peptide levels (930 pg/mL (RV<75)) and the pathology report (PNET tumor grade 2). Two years after the surgery, the patient was asymptomatic, and no residual lesions or metastases were evident in a control MRI. Conclusion: Late diagnosis of VIPoma is associated with worsened quality of life, severe complications, and high prevalence of metastasis. Therefore, it should be suspected in patients with chronic secretory diarrhea that is not caused by an infection, since early diagnosis and timely treatment can contribute to achieving better survival rates in these patients.

Avoiding Pitfalls in Insulinomas by Preoperative Localization with a Dual Imaging Approach

Insulinomas are rare endocrine malignancies of the pancreas that require surgical resection but can be difficult to localize preoperatively. We sought to review and improve the accuracy of preoperative localization techniques at our institution. We retrospectively reviewed all insulinomas that underwent resection at our institution between 1998 and 2016. Localization techniques include selective arterial calcium stimulation (CaStim), CT, MRI, angiography, and somatostatin receptor scintigraphy. Thirty-eight patients had pathologically proven insulinomas on surgical resection. Localization accuracies of CaStim, CT, and MRI were 89 per cent (31/35), 67 per cent (22/33), and 46 per cent (11/24), respectively. When compared with CTalone and CaStim alone, the combination of these two modalities resulted in 100 per cent preoperative localization (30/30), whereas the use of CaStim alone resulted in 80 per cent (4/5) localization and the use of CT alone resulted in 66 per cent (2/3) localization. Four of our patients had both negative CT and MRI. Among these patients, CaStim was 100 per cent localizing and the only positive modality for these patients. These data confirm that CaStim is accurate in preoperatively identifying single and multiple insulinomas; and when combined with CT, this accuracy is increased to 100 per cent. Based on these data, we propose that a dual imaging approach is a superior means of preoperative localization.

Octreotide Nanoparticles Showed Affinity for In Vivo MIA Paca-2 Inducted Pancreas Ductal Adenocarcinoma Mimicking Pancreatic Polypeptide-Secreting Tumor of the Distal Pancreas (PPoma)

PURPOSE

Pancreatic Polypeptide-secreting tumor of the distal pancreas (PPoma) is a rare, difficult and indolent type of cancer with a survival rate of 5-year in only 10% of all cases. The PPoma is classified as a neuroendocrine tumor (NET) not functioning that overexpresses SSTR 2 (somatostatin receptor subtype 2). Thus, in order to improve the diagnosis of this type of tumor, we developed nanoparticulate drug carriers based on poly-lactic acid (PLA) polymer loaded with octreotide and radiolabeled with Technetium-99 m (99mTc).

METHODS

PLA/PVA octreotide nanoparticles were developed by double-emulsion technique. These nanoparticles were characterized by Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) and radiolabeled with 99mTc by the direct via forming 99mTc-PLA/PVA octreotide nanoparticles. The safety of these nanosystems was evaluated by the MTT cell toxicity assay and their in vivo biodistribution was evaluated in xenografted inducted animals.

RESULTS

The results showed that a 189 nm sized nanoparticle were formed with a PDI of 0,097, corroborating the monodispersive behavior. These nanoparticles were successfully radiolabeled with 99mTc showing uptake by the inducted tumor. The MTT assay corroborated the safety of the nanosystem for the cells.

CONCLUSION

The results support the use of this nanosystem (99mTc-PLA/PVA octreotide nanoparticles) as imaging agent for PPoma. Graphical Abstract Polypeptide-Secreting Tumor of the Distal Pancreas (PPoma) Radiolabeled Nanoparticles for Imaging.

Plasma Pancreastatin Predicts the Outcome of Surgical Cytoreduction in Neuroendocrine Tumors of the Small Bowel

OBJECTIVES

Elevated pancreastatin (PST) levels have been shown to be associated with poor prognosis in small bowel neuroendocrine tumors (NETs). We hypothesized that plasma PST levels that remain elevated following surgical cytoreduction portend a poor prognosis in well-differentiated small bowel NETs.

METHODS

Patients diagnosed with small bowel NETs who underwent surgical cytoreduction at our institution were identified. Demographics, histopathologic characteristics, and biochemical data were collected. Only patients who had serial preoperative PST (PreopPST) and postoperative PST (PostopPST) levels were included in this study. Patients were sorted into groups by PST level to assess their response to surgical cytoreduction (group 1, PreopPST/PostopPST normal; group 2, PreopPST elevated/PostopPST normal; group 3, PreopPST/PostopPST elevated). Survival rates were calculated from the date of surgery.

RESULTS

PreopPST and PostopPST levels were collected from 300 patients. Patients in groups 1 (n = 74) and 2 (n = 81) had a significant survival advantage compared with patients in group 3 (n = 145) (P < 0.0001). Kaplan-Meier 5- and 10-year survival rates were as follows: group 1: 93% and 82%; group 2: 91% and 65%; and group 3: 58% and 34%, respectively.

CONCLUSIONS

Serial monitoring of plasma PST is useful in predicting long-term survival following surgical cytoreduction and can be helpful to identify patients who have a poor prognosis.

PET/MR Imaging of the Pancreas

PET/MR imaging has the potential to markedly alter pancreatic care in both the malignant, and premalignant states with the ability to perform robust, high-resolution, quantitative molecular imaging. The ability of PET/MR imaging to monitor disease processes, potentially correct for motion in the upper abdomen, and provide novel biomarkers that may be a combination of MR imaging and PET biomarkers, offers a unique, precise interrogation of the pancreatic milieu going forward.

Plasma Neurokinin A Levels Predict Survival in Well-Differentiated Neuroendocrine Tumors of the Small Bowel

OBJECTIVES

Elevated neurokinin A (NKA) levels are associated with poor prognosis in patients with small bowel neuroendocrine tumors. We hypothesized that patients with NKA levels that remain elevated despite treatment with surgical cytoreduction have a poor prognosis.

METHODS

Patients diagnosed with small bowel neuroendocrine tumors who underwent surgical cytoreduction at our institution were identified. Demographics, histopathologic characteristics, and biochemical data were collected. Patients were grouped by the trend of their NKA levels (group 1, continuously normal; group 2, transiently elevated but normalized after therapy; group 3, remained elevated despite therapy). Survival rates were calculated from the date of the patient's first NKA level.

RESULTS

Serial NKA values after surgical cytoreduction were monitored in 267 patients. Kaplan-Meier 2-year, 5-year, and 10-year survival rates were as follows: group 1 (n = 157), 97%, 89%, and 62%; group 2 (n = 78), 99%, 90%, and 78%; and group 3 (n = 32), 88%, 69%, and 0%. Survival rates were statistically significant between groups 1 and 3 and between groups 2 and 3 (P < 0.01).

CONCLUSIONS

Serial monitoring of plasma NKA levels is useful in identifying patients who have a poor prognosis. Elevated NKA levels can indicate the need for immediate therapeutic intervention.

PPoma Review: Epidemiology, Aetiopathogenesis, Prognosis and Treatment

Generally, pancreatic polypeptide-secreting tumor of the distal pancreas (PPoma) is classified as a rare tumor, and may occur sporadically or be associated in families or with multiple endocrine neoplasia type 1 (NEM 1). It grows slowly, reaching large dimensions at the time of diagnosis and the symptomatology is fundamentally due to the mass effect, causing either non-specific abdominal pain or symptoms suggestive of obstruction of the pancreatic or biliary duct. Therefore, when detected, they are usually malignant, with metastases mainly in the liver. The combination of serum analysis of increased levels of chromogranin A and pancreatic polypeptide and pancreastatin is very useful with a sensitivity of up to 95%. However, in addition, scintigraphicexams with somatostatin analogues should be performed to better clarify the diagnosis. Surgical resection is the treatment of choice, despite surgical difficulty and because they are generally palliative due to the metastases. Surgeries for tumor volume reduction are also performed to relieve symptoms. Chemotherapy commonly uses streptozotocin and somatostatin analogues to treat residual disease. Unfortunately, the survival rates are still very low, less than 10%, and if metastases already exist, this percentage drops to 3%.

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.

The role of pre-operative imaging and double balloon enteroscopy in the surgical management of small bowel neuroendocrine tumors: Is it necessary?

BACKGROUND AND OBJECTIVES

Pre-operative localization of small bowel neuroendocrine tumors (SBNET) is important for operative planning. The aim was to determine the effectiveness of pre-operative imaging and double-balloon enteroscopy (DBE) in identifying extent of disease.

METHODS

Database review identified 85 patients with primary SBNET between 2006 and 2013. Analysis included patients who underwent imaging, endoscopy, and surgery at our institution.

RESULTS

Average age was 60.7 years. Sixty-six (77.1%) patients had a primary NET in the ileum. Seventy-two patients (67.3%) underwent CT, 47 (46.7%) had MRI, 44 (46.7%) had somatostatin receptor imaging (SRI), and 41 (39.3%) underwent DBE. The sensitivity of each in identifying the NET was 59.7% for CT, 54% for MRI, 56% for SRI, and 88.1% for DBE. Eighteen (21.2%) patients had primary tumors not identified on imaging. Of these 18, 13 underwent DBE, and 12 of 13 (92.3%) DBEs identified the primary lesion. DBE was significantly better at identifying the primary NET than CT, MRI or SRI (P = 0.004, 0.007, and 0.012).

CONCLUSIONS

Most SBNETs are identified with a combination of imaging modalities. In those with unidentified primary tumors after imaging, DBE should be considered as it may provide valuable information as to the location of the primary tumor.

The Surgical Management of Small Bowel Neuroendocrine Tumors: Consensus Guidelines of the North American Neuroendocrine Tumor Society

Small bowel neuroendocrine tumors (SBNETs) have been increasing in frequency over the past decades, and are now the most common type of small bowel tumor. Consequently, general surgeons and surgical oncologists are seeing more patients with SBNETs in their practices than ever before. The management of these patients is often complex, owing to their secretion of hormones, frequent presentation with advanced disease, and difficulties with making the diagnosis of SBNETs. Despite these issues, even patients with advanced disease can have long-term survival. There are a number of scenarios which commonly arise in SBNET patients where it is difficult to determine the optimal management from the published data. To address these challenges for clinicians, a consensus conference was held assembling experts in the field to review and discuss the available literature and patterns of practice pertaining to specific management issues. This paper summarizes the important elements from these studies and the recommendations of the group for these questions regarding the management of SBNET patients.

Cardiac Surgery for Carcinoid Heart Disease: A Weapon Not to Be Misused

Carcinoid heart disease (CHD) complicates approximately 25% of patients with a carcinoid tumor and carcinoid syndrome and leads to heart valve degeneration with mixed-stenotic and regurgitation pathology and consequent heart failure (HF) leading to significant morbidity and mortality. Cardiac surgery in symptomatic, severe CHD leads to significantly better functional capacity and prolonged survival when compared to medical treatment alone. Recent studies have shown improvement in postoperative outcomes of patients undergoing surgery for CHD over the last decades. The trend for early diagnosis and application of surgery prior to the manifestation of HF symptoms, which tended to develop during the previous years, does not seem justifiable based on the findings of recent studies. Therefore, the optimal timing of intervention in CHD and the type of valve that should preferably be used remain issues of controversy. This review comprehensively examines the existing literature on the treatment options for patients with CHD, with a special focus on short- and long-term survival after cardiac surgery, and discusses the selection of the exact patient profile and intervention timing that are more likely to optimize the benefit-to-risk ratio for surgical intervention.

Management of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (pNETs) are rare tumors that have a better prognosis than their exocrine counterpart, but frequently present with advanced disease. Management of pNETs has evolved considerably over the past decade. Surgical resection remains the only potentially curative option for patients with pNETs. Patients who have locoregionally advanced and/or metastatic pNETs require additional treatments. These include liver-directed (transarterial (chemo)-embolization, selective intraarterial radio therapy) and systemic therapies (somatostatin analogs, targeted therapy such as tyrosine-kinase inhibitors and mammalian target of rapamycin inhibitor, peptide receptor radionuclide therapy and cytotoxic chemotherapy). The aim of this article is to review the current treatment options as well as potential future therapeutic perspectives for patients with pNETs.