Will clinical heterogeneity of neuroendocrine tumors impact their management in the future? Lessons from recent trials

Response heterogeneity as a new biomarker of treatment response in patients with neuroendocrine tumors

Aim: The RAISE project aimed to find a surrogate end point to predict treatment response early in patients with enteropancreatic neuroendocrine tumors (NET). Response heterogeneity, defined as the coexistence of responding and non-responding lesions, has been proposed as a predictive marker for progression-free survival (PFS) in patients with NETs. Patients & methods: Computerized tomography scans were analyzed from patients with multiple lesions in CLARINET (NCT00353496; n = 148/204). Cox regression analyses evaluated association between response heterogeneity, estimated using the standard deviation of the longest diameter ratio of target lesions, and NET progression. Results: Greater response heterogeneity at a given visit was associated with earlier progression thereafter: week 12 hazard ratio (HR; 95% confidence interval): 1.48 (1.20-1.82); p < 0.001; n = 148; week 36: 1.72 (1.32-2.24); p < 0.001; n = 108. HRs controlled for sum of longest diameter ratio: week 12: 1.28 (1.04-1.59); p = 0.020 and week 36: 1.81 (1.20-2.72); p = 0.005. Conclusion: Response heterogeneity independently predicts PFS in patients with enteropancreatic NETs. Further validation is required.

Virus-associated neuroendocrine cancers: Pathogenesis and current therapeutics

Neuroendocrine neoplasms (NENs) comprise malignancies involving neuroendocrine cells that often lead to fatal pathological conditions. Despite escalating global incidences, NENs still have poor prognoses. Interestingly, research indicates an intricate association of tumor viruses with NENs. However, there is a dearth of comprehension of the complete scenario of NEN pathophysiology and its precise connections with the tumor viruses. Interestingly, several cutting-edge experiments became helpful for further screening of NET for the presence of polyomavirus, Human papillomavirus (HPV), Kaposi sarcoma-associated herpesvirus (KSHV), Epstein Barr virus (EBV), etc. Current research on the neuroendocrine tumor (NET) pathogenesis provides new information concerning their molecular mechanisms and therapeutic interventions. Of note, scientists observed that metastatic neuroendocrine tumors still have a poor prognosis with a palliative situation. Different oncolytic vector has already demonstrated excellent efficacies in clinical studies. Therefore, oncolytic virotherapy or virus-based immunotherapy could be an emerging and novel therapeutic intervention. In-depth understanding of all such various aspects will aid in managing, developing early detection assays, and establishing targeted therapeutic interventions for NENs concerning tumor viruses. Hence, this review takes a novel approach to discuss the dual role of tumor viruses in association with NENs' pathophysiology as well as its potential therapeutic interventions.

Surgical Feasibility, Determinants, and Overall Efficacy of Neoadjuvant 177Lu-DOTATATE PRRT for Locally Advanced Unresectable Gastroenteropancreatic Neuroendocrine Tumors

We assessed 177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) in the neoadjuvant setting in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs). We also evaluated the variables associated with resectability of the primary tumor after PRRT. Methods: This study included 57 GEP-NET patients who had a primary tumor that was unresectable (because of vascular involvement as defined using the pancreatic ductal adenocarcinoma criteria of the National Comprehensive Cancer Network) and who underwent 177Lu-DOTATATE therapy without any prior surgery. They were categorized into 2 groups: 23 patients without liver metastases (group 1) and 34 patients with potentially resectable liver metastases (group 2). 177Lu-DOTATATE was administered with mixed amino acid-based renal protection at a dose of 7.4 GBq (200 mCi) per cycle. Surgical resectability was evaluated using triphasic contrast-enhanced abdominal CT imaging at 3 different time points during the PRRT course. Four broad categories of overall PRRT response were evaluated. The Kaplan-Meier product-limit method was used to calculate progression-free survival (PFS) and overall survival (OS). Associations between variables and a resectable primary tumor after PRRT were analyzed using the χ2 test, with a P value of less than 0.05 considered statistically significant. Results: After 177Lu-DOTATATE therapy, the unresectable primary tumor became resectable in 15 of 57 (26.3%) patients (7 patients in group 1 and 8 patients in group 2). A complete or partial response to PRRT was seen in 48 patients (84%), 23 patients (40%), 18 patients (31%), and 23 patients (40%) using symptomatic, biochemical, molecular imaging, and anatomic imaging criteria, respectively. Estimated rates of PFS were 95% and 90% at 2 y in groups 1 and 2, respectively. The 2-y OS of the 2 groups combined was 92.1%. The rate at which the primary tumor was resectable after PRRT was significantly higher in patients who had duodenal neuroendocrine tumors, patients who had GEP-NETs with no regional lymph node involvement, patients for whom the primary tumor was smaller than 5 cm, patients for whom liver metastases were no larger than 1.5 cm, patients for whom there were no more than 3 liver metastases, and patients for whom 18F-FDG uptake in the primary tumor had an SUVmax of less than 5. Conclusion: In a moderate fraction of GEP-NET patients, with or without liver metastases, whose primary tumor was unresectable because of vascular involvement, the primary tumor converted from unresectable to resectable after 177Lu-DOTATATE therapy, signifying that neoadjuvant PRRT can be considered in such patients. The effective control of symptoms, favorable morphologic and functional imaging response, and durable PFS and OS that we observed after 177Lu-DOTATATE PRRT may lead to less morbidity and mortality in these patients.

Differential methylation of G-protein coupled receptor signaling genes in gastrointestinal neuroendocrine tumors

Neuroendocrine tumors (NETs) of the small intestine undergo large chromosomal and methylation changes. The objective of this study was to identify methylation differences in NETs and consider how the differentially methylated genes may impact patient survival. Genome-wide methylation and chromosomal copy number variation (CNV) of NETs from the small intestine and appendix were measured. Tumors were divided into three molecular subtypes according to CNV results: chromosome 18 loss (18LOH), Multiple CNV, and No CNV. Comparison of 18LOH tumors with MultiCNV and NoCNV tumors identified 901 differentially methylated genes. Genes from the G-protein coupled receptor (GPCR) pathways are statistically overrepresented in the differentially methylated genes. One of the highlighted genes from the GPCR pathway is somatostatin (SST), a clinical target for NETs. Patient survival based on low versus high methylation in all samples identified four significant genes (p < 0.05) OR2S2, SMILR, RNU6-653P, and AC010543.1. Within the 18LOH molecular subtype tumors, survival differences were identified in high versus low methylation of 24 genes. The most significant is TRHR (p < 0.01), a GPCR with multiple FDA-approved drugs. By separating NETs into different molecular subtypes based on chromosomal changes, we find that multiple GPCRs and their ligands appear to be regulated through methylation and correlated with survival. These results suggest opportunities for better treatment strategies for NETs based on molecular features.

Clinical Utility of 18F-FDG PET in Neuroendocrine Tumors Prior to Peptide Receptor Radionuclide Therapy: A Systematic Review and Meta-Analysis

Simple Summary

Functional imaging with ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) has evolved into a major clinical tool in cancer diagnosis and management for many malignancies in diverse clinical settings, providing valuable information on tumor behavior and aggressiveness. In the field of neuroendocrine tumors (NETs), recent advances in molecular imaging and targeted treatments with novel theranostic agents favor a more patient-tailored approach. Although peptide receptor radionuclide therapy (PRRT) has recently become an established therapy for progressive NETs, the role of ¹⁸F-FDG PET prior to PRRT in patients with NETs of different origins and grades remains to be determined. Herein, we provide a comprehensive summary of available evidence in contemporary literature by means of a systematic review and meta-analysis, demonstrating that dual-functional imaging with ⁶⁸Ga-DOTA-peptides and ¹⁸F-FDG prior to PRRT appears to be a useful tool in NET management by delineating tumor somatostatin receptor expression and glycolytic metabolic activity, and predicting tumor response and survival outcomes.

Abstract

The role of ¹⁸F-FDG PET in patients with variable grades of neuroendocrine tumors (NETs) prior to peptide receptor radionuclide therapy (PRRT) has not been adequately elucidated. We aimed to evaluate the impact of ¹⁸F-FDG PET status on disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) in neuroendocrine tumor (NET) patients receiving PRRT. We searched the MEDLINE, Embase, Cochrane Library, and Web of Science databases up to July 2020 and used the Newcastle-Ottawa scale (NOS) criteria to assess quality/risk of bias. A total of 5091 articles were screened. In 12 studies, 1492 unique patients with NETs of different origins were included. The DCR for patients with negative ¹⁸F-FDG PET status prior to PRRT initiation was 91.9%, compared to 74.2% in patients with positive ¹⁸F-FDG PET status (random effects odds ratio (OR): 4.85; 95% CI: 2.27–10.36). Adjusted analysis of pooled hazard ratios (HRs) confirmed longer PFS and OS in NET patients receiving PRRT with negative ¹⁸F-FDG PET (random effects HR:2.45; 95%CIs: 1.48–4.04 and HR:2.25; 95% CIs:1.55–3.28, respectively). In conclusion, ¹⁸F-FDG PET imaging prior to PRRT administration appears to be a useful tool in NET patients to predict tumor response and survival outcomes and a negative FDG uptake of the tumor is associated with prolonged PFS and OS.

Initial clinical evaluation of indigenous 90Y-DOTATATE in sequential duo-PRRT approach (177Lu-DOTATATE and 90Y-DOTATATE) in neuroendocrine tumors with large bulky disease: Observation on tolerability, 90Y-DOTATATE post- PRRT imaging characteristics (bremsstrahlung and PETCT) and early adverse effects

¹⁷⁷Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) alone has lesser potential in the clinical setting of neuroendocrine tumor (NET) with large bulky disease and nonhomogeneous somatostatin receptors (SSTR) distribution, owing to lower energy (Eβmax 0.497 MeV) and a shorter particle penetration range (maximum 2–4 mm) of ¹⁷⁷Lu. In large bulky NETs, ⁹⁰Yttrium (⁹⁰Y) has the theoretical advantages because of a longer beta particle penetration range (a maximum soft tissue penetration of 11 mm). Therefore, a combination of ¹⁷⁷Lu and ⁹⁰Y is a theoretically sound concept that can result in better response in metastatic NET with large-bulky lesion and non-homogeneous SSTR distribution. The aim of the study was to determine the feasibility of combining ⁹⁰Y-DOTATATE with ¹⁷⁷Lu-DOTATATE PRRT as sequential duo-PRRT in metastatic NET with (≥5 cm) including the post ⁹⁰Y-DOTATATE-PRRT imaging and also to determine early toxicity of the duo-PRRT approach. A total of 9 patients received combination of ¹⁷⁷Lu-DOTATATE with ⁹⁰Y-DOTATATE (indigenously prepared and approved) through sequential duo-PRRT approach. These 9 NET patients were included and analyzed in this study. All 9 patients had undergone post-PRRT ⁹⁰Y-DOTATATE imaging, including a whole-body planar bremsstrahlung imaging followed by regional single-photon emission computed tomography (SPECT)-computed tomography (CT) imaging and also a regional positron emission tomography–computed tomography imaging. Grading of ⁹⁰Y-DOTATATE and ¹⁷⁷Lu-DOTATATE uptake was done on post-PRRT imaging by both modalities. The size of the lesions ranged from 5.5 cm to 16 cm with average size of 10 cm before sequential duo-PRRT was decided. Sequential duo-PRRT was administered because of stable, unresponsive disease following ¹⁷⁷Lu-DOTATATE in 5 patients (55.6%), progressive disease after ¹⁷⁷Lu-DOTATATE in 2 patients (22.2%), and with neoadjuvant intent in 2 patients (22.2%). The total cumulative dose of ¹⁷⁷Lu-DOTATATE before duo-pRRT ranged from 11.84 GBq to 37 GBq per patient and average administered dose of 27.21 GBq per patient in this study. Out of 9 patients, 8 patients received single cycle of ⁹⁰Y-DOTATATE (ranging from 2.66 GBq to 3.4 GBq per patient with average administered dose of 3.12 GBq per patient). One patient received two cycles of ⁹⁰Y-DOTATATE (total dose of 6.2 GBq). Out of 9 patients, 8 patients showed excellent tracer concentration in lesions on post-PRRT ⁹⁰Y-DOTATATE imaging and the remaining 1 patient showed fairly adequate ⁹⁰Y-DOTATATE tracer uptake in lesion on visual analysis. There was matched ⁹⁰Y-DOTATATE uptake with ⁶⁸Ga-DOTATATE and also with ¹⁷⁷LuDOTATATE in all 9 patients. The sequential duo-PRRT was well tolerated by all patients. Two patients (22.2%) developed mild nausea, one patient (11.1%) developed transient mild-grade hemoglobin toxicity, and one patient (11.1%) developed mild-grade gastrointestinal symptoms (loose motion and abdominal pain). No nephrotoxicity, hepatotoxicity, and other hematological toxicity was observed. The combination of the indigenous ⁹⁰Y-DOTATATE with ¹⁷⁷Lu-DOTATATE PRRT in NET as sequential duo-PRRT was well tolerated, feasible and safe in stable, unresponsive/progressive disease following single isotope ¹⁷⁷Lu-DOTATATE therapy and also in neoadjuvant PRRT setting with large bulky lesion (≥≥5cm). Post-PRRT ⁹⁰Y-DOTATATE imaging showed excellent ⁹⁰Y-DOTATATE uptake in nearly all NET patients. Mild-grade early adverse effects were easily manageable and controllable in this sequential duo-PRRT approach.

Clinical and Translational Research Challenges in Neuroendocrine Tumours

Neuroendocrine tumours (NETs) represent a range of neoplasms that may arise from any (neuro)endocrine cell situated in any part of the human body. As any other rare diseases, NETs face several difficulties in relation to research. This review will describe some of the main challenges and proposed solutions faced by researchers with expertise in rare malignancies. Some of the most common challenges in clinical and translational research are enumerated in this review, covering aspects from clinical, translational and basic research. NETs being a heterogeneous group of diseases and a limited sample size of clinical and translational research projects are the main challenges. Challenges with NETs lay over the disparities between healthcare models to tackle rare diseases. NETs add an extra layer of complexity due to a numerous group of different entities. Prospective real-world data trials are an opportunity for rare cancers with the revolution of electronic health technologies. This review explores potential solutions to these challenges that could be useful not only to the NET community but also to other rare tumours researchers.

Clinicopathological heterogeneity between primary and metastatic sites of gastroenteropancreatic neuroendocrine neoplasm

Background

Chromogranin A (CgA), synaptophysin (Syn) and the Ki-67 index play significant roles in diagnosis or the evaluation of the proliferative activity of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). However, little is known about whether these biological markers change during tumor metastasis and whether such changes have effect on prognosis.

Methods

We analyzed 35 specimens of both primary and metastatic tumor from 779 patients who had been diagnosed as GEP-NENs at Wuhan Union Hospital from August 2011 to October 2019. The heterogeneity of CgA, Syn and Ki-67 index was evaluated by immunohistochemical analysis.

Results

Among these 779 patients, the three most common sites of NENs in the digestive tract were the pancreas, rectum and stomach. Metastases were found in 311 (39.9%) patients. Among the 35 patients with both primary and metastatic pathological specimens, differences in the Ki-67 level were detected in 54.3% of the patients, while 37.1% showed a difference in CgA and only 11.4% showed a difference in Syn. Importantly, due to the difference in the Ki-67 index between primary and metastatic lesions, the WHO grade was changed in 8.6% of the patients. In addition, a Kaplan–Meier survival analysis showed that patients with Ki-67 index variation had a shorter overall survival (p = 0.0346), while neither Syn variation nor CgA variation was related to patient survival (p = 0.7194, p = 0.4829).

Conclusions

Our data indicate that primary and metastatic sites of GEP-NENs may exhibit pathological heterogeneity. Ki-67 index variation is closely related to the poor prognosis of patients with tumor metastasis, but neither Syn variation nor CgA variation is related to patient prognosis. Therefore, clinicopathologic evaluation of the primary tumor and metastatic sites could be helpful for predicting the prognosis.

Early life exposures associated with risk of small intestinal neuroendocrine tumors

Small intestinal neuroendocrine tumors (SINT) are rare with incidence increasing over the past 40 years. The purpose of this work is to examine the role of environmental exposures in the rise of SINT incidence using the Utah Population Database, a resource of linked records including life events, cancer diagnoses and residential histories. SINT cases born in Utah were identified through the Utah Cancer Registry with: diagnosis years of 1948 to 2014 and age at diagnosis of 23 to 88 years. Controls were matched to cases 10:1 based on sex, birth year and residence time in Utah. Cases and controls were geocoded to their birth locale. An isotonic spatial scan statistic was used to test for the occurrence and location(s) of SINT clusters. Potential environmental exposures and economic conditions in the birth locales at the time of the birth (1883–1982) were generated using historical references. Conditional logistic regression was used to estimate odd ratios. We report a spatial cluster central to historic coal mining communities, associated with a 2.86 relative risk (p = 0.016) of SINT. Aspatial analyses of industry and mining exposures further suggest elevated risk for early life exposure near areas involved in the construction industry (OR 1.98 p = 0.024). Other exposures approached significance including coal, uranium and hard rock mining during the earliest period (1883–1929) when safety from exposures was not considered. We do observe a lower risk (OR 0.58 p = 0.033) associated with individuals born in rural areas in the most recent period (1945–1982). Environmental exposures early in life, especially those from industries such as mining, may confer an elevated risk of SINT.

Effect of the Tryptophan Hydroxylase Inhibitor Telotristat on Growth and Serotonin Secretion in 2D and 3D Cultured Pancreatic Neuroendocrine Tumor Cells

Serotonin, a biologically active amine, is related to carcinoid syndrome in functioning neuroendocrine tumors (NETs). Telotristat ethyl is a novel inhibitor of the tryptophan hydroxylase (TPH), a key enzyme in the production of serotonin. While its use in patients with carcinoid syndrome and uncontrolled diarrhea under somatostatin analogs (SSAs) has been recently approved, in vitro data evaluating its effectiveness are lacking. For this reason, we aimed to evaluate the effect of telotristat as monotherapy, and in combination with SSAs, on proliferation and secretion in a NET cell line model. The human pancreatic NET cell lines BON-1/QGP-1 were used as 2D and 3D cultured models; somatostatin receptor and TPH mRNA expression, as well as the potential autocrine effect of serotonin on tumor cell proliferation using a 3D culture system were evaluated. Telotristat decreased serotonin production in a dose-dependent manner at a clinically feasible concentration, without affecting cell proliferation. Its combination with pasireotide, but not with octreotide, had an additive inhibitory effect on serotonin secretion. The effect of telotristat was slightly less potent, when BON-1 cells were co-treated with octreotide. Octreotide and pasireotide had no effect on the expression of TPH. Telotristat did not have an effect on mRNA expression of somatostatin receptor subtypes. Finally, we showed that serotonin did not have an autocrine effect on NET cell proliferation on the 3D cell model. These results suggest that telotristat is an effective drug for serotonin inhibition, but the effectiveness of its combination with SST2 (somatostatin receptor subtype 2)-preferring SSA should be evaluated in more detail.

Concordance Between the Ki-67 Index Cutoff Value of 55% and Differentiation in Neuroendocrine Tumor and Neuroendocrine Carcinoma in Grade 3 Pancreatic Neuroendocrine Neoplasms

OBJECTIVE

In 2017 and 2019, the World Health Organization defined grade 3 neuroendocrine tumors (G3 NETs) and neuroendocrine carcinoma (G3 NEC) in the pancreas. The validity of this classification remains to be verified.

METHODS

Clinical data were collected and analyzed for 39 G3 pancreatic neuroendocrine neoplasms (PanNENs) patients between 2009 and 2018.

RESULTS

The tumor-node-metastasis stage (P = 0.0260), differentiation (P = 0.0115), and Ki-67 index (P = 0.0371) are prognostic factors for G3 PanNENs by Kaplan-Meier survival analysis. Among 39 patients, 18 had a Ki-67 index of less than 55% and well-differentiated morphology (G3 NET) and 16 had a Ki-67 index of 55% or greater and poorly differentiated morphology (G3 NEC). Grade 3 neuroendocrine tumor had a significant better prognosis than G3 NEC (median overall survival time, 25 months [95% confidence interval, 10.854-39.146 months] vs 12 months [95% confidence interval, 6.316-17.684 months], P = 0.0164). Based on Cox regression analyses, tumor-node-metastasis stage (P = 0.016) was identified as the independent prognostic factor for G3 PanNENs.

CONCLUSIONS

The upper Ki-67 index cutoff of 55% might be the best cutoff value to define G3 NETs and G3 NECs for G3 PanNENs. The World Health Organization 2017 and 2019 classification system for G3 PanNENs can identify high-risk patients with G3 PanNENs.

Current progress in the clinical use of circulating tumor cells as prognostic biomarkers

The process of metastasis is characterized by the shedding of tumor cells into the bloodstream, where they are transported to other parts of the body to seed new tumors. These cells, known as circulating tumor cells (CTCs), have the potential to reveal much about an individual cancer case, and theoretically can aid in the prediction of outcomes and design of precision treatments. Recent advances in technology now allow for the robust and reproducible characterization of CTCs from a simple blood draw. Both the number of circulating cells and important molecular characteristics correlated with clinical phenotypes such as drug resistance can be obtained and used for real-time prognostic analysis. Molecular characterization can provide a snapshot of the activity of the main tumor (serving as a "liquid biopsy") and early warnings concerning changes such as the development of resistance, and aid in predicting the efficacy of different therapeutic approaches for treatment optimization. Herein, the authors review the current clinical use of CTCs as prognostic biomarkers for several different cancers. The quantification of CTCs can lead to more accurate staging and decision making regarding options such as adjuvant chemotherapy.

Effects of Ketoconazole on ACTH-Producing and Non-ACTH-Producing Neuroendocrine Tumor Cells

Prolonged remission of hypercortisolism with steroidogenesis inhibitors has been described in patients with ectopic adrenocorticotropic hormone (ACTH) syndrome. The anti-proliferative and pro-apoptotic effect of ketoconazole in human cancer cells was previously suggested. The aim of this study was to explore the effects of ketoconazole on ACTH-producing and non-ACTH-producing neuroendocrine tumor (NET) cell lines. The effects of ketoconazole alone, and in combination with somatostatin analogs, were evaluated in two human cell lines: DMS-79 (ectopic ACTH-producing small cell lung carcinoma) and BON-1 (human pancreatic NET). Total DNA measurement, apoptosis, cell cycle, chromogranin A (CgA)/proopiomelanocortin (POMC) expression by qRT-PCR, serotonin, CgA, and ACTH secretion assays were performed. In both cell lines, ketoconazole significantly suppressed cell growth and colony formation in a dose and time-dependent manner. The effect in DMS-79 was primarily cytotoxic, while it was more apoptotic in BON-1 cells. Ketoconazole also induced increase in G0/G1 phase in both cell lines and arrest in phase G2/M of BON-1 cells. Ketoconazole did not affect the secretion of serotonin, CgA, ACTH, or the mRNA expression of CgA and POMC. Decreased serotonin secretion was observed after the combination treatment with pasireotide. These results suggest a direct effect of ketoconazole on cell proliferation, apoptosis, and cell cycle in both ACTH- and non-ACTH-producing NET cells.

Neuroendocrine Tumor Therapy with Lutetium-177: A Literature Review

The worldwide incidence of neuroendocrine tumors (NETs) has been increasing. They are a very diverse group of tumors which are commonly found in the gastrointestinal and bronchopulmonary tracts. These tumors usually express somatostatin receptors. Therefore, somatostatin analogs are used for symptom relief as well as treatment. Of the many therapeutic options available, peptide receptor radionuclide therapy (PRRT) has been shown to be very promising. In January 2018, the Food Drug and Authority (FDA) approved 177Lu-Dotatate for use in gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Lutetium is a lower energy beta-emitting radionuclide. The therapeutic use of lutetium-177 (177Lu) has shown better results in advanced gastroenteropancreatic and bronchial neuroendocrine tumors when compared with other therapies available. Adverse effects associated with this therapy include myelotoxicity and nephrotoxicity as the radiopeptides are reabsorbed and accumulate in the renal interstitium. Everolimus is a good and safe option in patients pretreated with 177Lu-Dotatate. Lutetium, in combination with somatostatin analogs, has proven efficacy to treat gastroenteropancreatic neuroendocrine tumors in candidates with somatostatin receptor-positive advanced tumors and normal renal function. This therapy has great potential as it decreases tumor size, improves symptoms, and improves quality of life.

Ghrelin-O-Acyltransferase (GOAT) Enzyme as a Novel Potential Biomarker in Gastroenteropancreatic Neuroendocrine Tumors

OBJECTIVES

The association between the presence and alterations of the components of the ghrelin system and the development and progression of neuroendocrine tumors (NETs) is still controversial and remains unclear.

METHODS

Here, we systematically evaluated the expression levels (by quantitative-PCR) of key ghrelin system components of in gastroenteropancreatic (GEP)-NETs, as compared to non-tumor adjacent (NTA; n = 42) and normal tissues (NT; n = 14). Then, we analyzed their putative associations with clinical-histological characteristics.

RESULTS

The results indicate that ghrelin and its receptor GHSR1a are present in a high proportion of normal tissues, while the enzyme ghrelin-O-acyltransferase (GOAT) and the splicing variants In1-ghrelin and GHSR1b were present in a lower proportion of normal tissues. In contrast, all ghrelin system components were present in a high proportion of tumor and NTA tissues. GOAT was significantly overexpressed (by quantitative-PCR (qPCR)) in tumor samples compared to NTA, while a trend was found for ghrelin, In1-ghrelin and GHSR1a. In addition, expression of these components displayed significant correlations with key clinical parameters. The marked overexpression of GOAT in tumor samples compared to NTA regions was confirmed by IHC, revealing that this enzyme is particularly overexpressed in gastrointestinal NETs, where it is directly correlated with tumor diameter.

CONCLUSIONS

These results provide novel information on the presence and potential pathophysiological implications of the ghrelin system components in GEP-NETs, wherein GOAT might represent a novel diagnostic biomarker.

Peptide Receptor Radiotherapy Comes of Age

Peptide receptor radionuclide therapy is a form of systemic radiotherapy shown to be effective in treating neuroendocrine tumors expressing somatostatin receptors. The NETTER-1 trial was the first randomized phase III clinical trial evaluating a radiolabeled somatostatin analog, and demonstrated significant improvement in progression-free survival among patients with midgut neuroendocrine tumors treated with ¹⁷⁷Lu-DOTATATE versus high-dose octreotide. This article discusses the evolution of peptide receptor radionuclide therapy, side effects, and potential future treatment approaches.

Variability of the Ki-67 proliferation index in gastroenteropancreatic neuroendocrine neoplasms - a single-center retrospective study

BACKGROUND

The Ki-67 index in gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) may change throughout the disease course. However, the definitive effect of Ki-67 variability on GEP-NENs remains unknown. The aims of this study were to evaluate changes in Ki-67 levels throughout the disease course and investigate the role of Ki-67 index variability in GEP-NENs.

METHODS

Specimens with multiple pathologies were evaluated from 30 patients who were selected from 514 patients with GEP-NENs, being treated at Wuhan Union Hospital from July 2009 to February 2018. The Ki-67 index was evaluated among multiple specimens over the disease course. Univariable and multivariable Cox proportional hazards regression analyses were performed to assess the prognostic significance of various clinical and histopathologic features.

RESULTS

Among the 514 patients with GEP-NENs, metastases were seen in 182 (35.41%). Among the 30 patients from whom specimens with multiple pathologies were obtained, 24 were both primary and metastatic specimens and six were specimens collected over the course of the disease. Changes in Ki-67 levels were detected in 53.3% of the patients, of whom 40% had up-regulated Ki-67 levels, and 13.3% had down-regulated Ki-67 levels. Kaplan-Meier survival analysis showed that the group with Ki-67 variability had a shorter overall survival (p = 0.0297). The Cox regression analysis indicated that Ki-67 variability (p = 0.038) was the only independent prognostic factor for overall survival.

CONCLUSIONS

Our data suggest that patients with GEP-NENs and Ki-67 variability had a poorer prognosis. The re-assessment of Ki-67 at sites of metastasis or during the disease course might play a role in predicting the prognosis of patients with GEP-NENs. This finding could have implications for how GEP-NENs are monitored and treated.

The IGF pathway is activated in insulinomas but downregulated in metastatic disease

Clinical and molecular studies have implicated epidermal growth factor receptor (EGFR), insulin-like growth factor (IGF) and target of rapamycin (mTOR) signaling pathways in the regulation of pancreatic neuroendocrine tumor (PanNET) growth. Interpretation and comparison of these studies is complex due to clinical and molecular tumor heterogeneity. We therefore focused in this study on insulinomas, which we examined for mRNA and protein expression of EGFR, IGF and mTOR signaling pathway components by quantitative real-time PCR (n=48) and immunohistochemistry (n=86). Findings were compared with normal pancreatic islets and correlated with histopathological data and clinical outcome. Insulinomas showed low EGFR and high IGF2 expression. IGFBP2, IGFBP3 and IGFBP6 mRNA levels were 2-4 folds higher than in islets. High protein expression of IGF2, IGF1R and INSR (in 51-92% of the tumors) and low to moderate expression of mTORC1 pathway proteins p-PS6k and p-4EBP1 (7-28% of the tumors) were observed. Correlations were found between 1) ERK1 mRNA expression and that of numerous IGF pathway genes, 2) p-ERK and IGF1R protein expression and 3) decrease of IGF pathway components and both metastatic disease and shorter 10 years disease free survival. In conclusion, our observations suggest that high expression of IGF signaling pathway components is a hallmark of insulinomas, but does not necessarily lead to increased mTOR signaling. Reduced expression of IGF pathway components may be an adverse prognostic factor in insulinomas.

Multilayered heterogeneity as an intrinsic hallmark of neuroendocrine tumors

Neuroendocrine tumors (NETs) comprise a complex and highly heterogeneous group of neoplasms that can arise all over the body, originating from neuroendocrine cells. NETs are characterized by a general lack of symptoms until they are in advanced phase, and early biomarkers are not as available and useful as required. Heterogeneity is an intrinsic, pivotal feature of NETs that derives from diverse causes and ultimately shapes tumor fate. The different layers that conform NET heterogeneity include a wide range of distinct characteristics, from the mere location of the tumor to its clinical and functional features, and from its cellular properties, to the core signaling and (epi)genetic components defining the molecular signature of the tumor. The importance of this heterogeneity resides in that it translates into a high variability among tumors and, hence, patients, which hinders a more precise diagnosis and prognosis and more efficacious treatment of these diseases. In this review, we highlight the significance of this heterogeneity as an intrinsic hallmark of NETs, its repercussion on clinical approaches and tumor management, and some of the possible factors associated to such heterogeneity, including epigenetic and genetic elements, post-transcriptional regulation, or splicing alterations. Notwithstanding, heterogeneity can also represent a valuable and actionable feature, towards improving medical approaches based on personalized medicine. We conclude that NETs can no longer be viewed as a single disease entity and that their diagnosis, prognosis and treatment must reflect and incorporate this heterogeneity.

Pretreatment hematologic markers as prognostic predictors of gastroenteropancreatic neuroendocrine tumors: a systematic review and meta-analysis

Background

Systemic inflammation can be reflected by peripheral hematologic parameters and combined index like the lymphocyte count, neutrophil count, platelet count, neutrophil-to-lymphocyte (NLR), and platelet-to-lymphocyte ratio (PLR). This systematic review and meta-analysis aimed to summarize the association between the hematologic markers and prognosis of gastroenteropancreatic neuroendocrine tumors (GEP–NETs).

Methods

A computerized systematic search of PubMed, Embase, and Web of Science was conducted up to August 2016. Studies evaluating prognosis value of hematologic parameters in patients with GEP–NETs were retrieved. For meta-analysis, hazard ratios (HRs) with 95% confidence intervals (95% CIs) were extracted and synthesized using Review Manager software.

Results

We identified eight retrospective cohort studies comprising a total of 724 cases. The majority of included studies focused on pancreatic neuroendocrine tumors (PNETs). The prognostic values of NLR, PLR, and platelet count were reported in six studies, two studies, and one study, respectively. All the parameters were associated with prognostic outcomes in patients with GEP–NETs. A high NLR was significantly associated with poor prognosis in GEP–NETs (pooled HR 3.05, 95% CI 1.96–4.76, I² = 0%, P < 0.00001 for overall survival (OS); pooled HR 3.30, 95% CI 2.04–5.32, I² = 0%, P < 0.00001 for recurrence-free survival [RFS]). In PNETs, pooled-analyses also showed significant superiority of a low NLR on OS (pooled HR 4.21, 95% CI 1.95–9.13, I² = 0%, P = 0.0003) and RFS (pooled HR 5.37, 95% CI 2.14–13.47, I² = 0%, P = 0.003).

Conclusions

These findings suggest that the elevated NLR could be an adverse prognosis factor for GEP–NETs. The conclusion should be mainly limited to PNETs as the majority of included cases were PNET patients. The prognostic value of other hematologic parameters deserves further investigation. We recommend that further studies should use a continuous NLR variable and adopt a prospective and matched study design.

Echocardiography in functional midgut neuroendocrine tumors: When and how often

The management of patients with midgut neuroendocrine tumors (MNET) is rapidly evolving. Current preoperative detection rates of primary tumor sites are higher than ever and progression-free survival in patients with already advanced disease is expanding due to the implementation of novel efficacious treatment strategies. This survival benefit may potentially translate into a need for a multidisciplinary approach to an even more heterogenous variety of clinical conditions, among these, carcinoid syndrome (CS) and carcinoid heart disease (CHD). The latter often triggers substantial morbidity and mortality, hence a systematic screening, an accurate diagnosis, as well as effective interventions are critically important. The rarity of the disease has result in a relative lack of statistically powerful evidence, which in turn may have rendered significant variability between practices. In this regard, despite recent guidelines, the optimal follow-up of patients with CHD remain debatable to some authors, perhaps due to the preponderance of certain schools throughout the manuscript. Herein, we present a concise and practical guidance document on clinical screening and echocardiographic surveillance of patients with CHD based on a comprehensive review of the literature, and complemented by our experience at the Center for Carcinoid and Neuroendocrine Tumors at The Mount Sinai Hospital.

Radionuclide Therapy for Neuroendocrine Tumors

Peptide receptor radionuclide therapy (PRRT) is a form of systemic radiotherapy that allows targeted delivery of radionuclides to tumor cells expressing high levels of somatostatin receptors. The two radiopeptides most commonly used for PRRT, ⁹⁰Y-DOTATOC and ¹⁷⁷Lu-DOTATATE, have been successfully employed for more than a decade for the treatment of advanced neuroendocrine tumors (NETs). Recently, the phase III, randomized NETTER-1 trial has compared ¹⁷⁷Lu-DOTATATE versus high-dose octreotide LAR in patients with progressive, metastatic midgut NETs, demonstrating exceptional tolerability and efficacy. This review summarizes recent developments in the field of radionuclide therapy for gastroenteropancreatic and lung NETs and considers possible strategies to further enhance its clinical efficacy.

Radionuclides in oncology clinical practice – review of the literature

Radionuclide therapy is a promising type of targeted therapy for cancer and its use is becoming more common in several types of malignant tumors.

Massive parallel sequencing and digital gene expression analysis reveals potential mechanisms to overcome therapy resistance in pulmonary neuroendocrine tumors

Background: Lung cancer is the leading cause of cancer-related deaths worldwide. 25% show neuroendocrine differentiation (typical/atypical carcinoids, large-/small-cell neuroendocrine carcinomas). Carcinoids present with long survival rates, but metastatic carcinoids correlate with decreased survival and are commonly insensitive to standard chemotherapy or radiation. Therefore, novel therapeutic strategies are urgently needed.

Material and methods: 70 representative tumor specimens were used for next-generation sequencing analysis of 14 genes related to therapy response. Additionally, mRNA-expression profiles of 60 matching samples were determined for 13 selected drug targets by using the NanoString nCounter technology.

Results: A number of features known to sensitize tumors for different targeted therapies could be identified, which hopefully improve the clinical management of this subgroup of lung neoplasias. In particular, EGFR expression was observed in the investigated tumors in a noteworthy manner. Additionally, MDM2 was strongly expressed in the majority of all samples whereas the expression of its physiological inhibitor, CDKN2A, was nearly absent in all low-grade tumors. TP53 showed a high frequency of variants in high-grade tumors but mutations were rare in carcinoids.

Conclusion: Based on our results, therapeutic approaches with MDM2-inhibitors and monoclonal anti-EGFR antibodies may be promising in pulmonary carcinoid tumors.