New strategies for advanced neuroendocrine tumors in the era of targeted therapy

Systemic Therapy for Pancreatic Neuroendocrine Tumors

Patients with metastatic or advanced pancreatic neuroendocrine tumors (NETs) carry poorer prognoses relative to patients with other NETs due to bulkier and often, more proliferative baseline disease. Patients with these tumors also possess more approved treatment options relative to patients with other NETs, making therapeutic sequencing nuanced. As such, defining optimal therapeutic sequencing and developing more potent cytoreductive treatments for patients are significant areas of research need in the field. Herein this review, we discuss the current systemic therapy landscape, our approach to therapeutic sequencing in the clinic and ongoing studies seeking to define optimal sequencing of systemic therapies, and novel therapeutics in development, for patients with pancreatic NETs. We limit the scope of this latter topic to agents with preclinical or clinical rationale over the last 8 years to provide a contemporary view of the drug development landscape and focus primarily on new types of peptide receptor radionuclide therapy, anti-vascular endothelial growth factor receptor tyrosine kinase inhibitors and anti-vascular endothelial growth receptor tyrosine kinase inhibitor plus immunotherapy combinations.

Efficacy and toxicity of anti-vascular endothelial growth receptor tyrosine kinase inhibitors in patients with neuroendocrine tumours - A systematic review and meta-analysis

AIM

Although anti-vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitors (RTKIs) have been tested in patients with neuroendocrine tumours (NETs) over the last two decades, no study to date has benchmarked efficacy and toxicity of these drugs in this patient population.

METHODS

All phase II and phase III studies of anti-VEGF RTKIs in patients with NETs, published between January 1, 2000 andJuly 31, 2021, across major trial databases, were searched in August 2021 for relevant studies. The primary objectives of the meta-analysis were to compare objective response rate (ORR) and progression-free survival (PFS) between patients with pancreatic NETs (pNETs) and extra-pancreatic NETs (epNETs), and the incidence rate ratio (IRR) of adverse events between patients receiving anti-VEGF RTKIs and control.

RESULTS

1611 patients were available for the meta-analysis; 1194 received anti-VEGF RTKIs. ORR in pNETs was 18% (95% confidence interval (CI) 13-25%), while ORR in epNETs was 8% (95% CI 5-12%); test for differences between pNETs and epNETs (x12 = 8.38, p < .01). Median PFS in pNETs was 13.9 months (95% CI 11.43-16.38 months), while median PFS in epNETs was 12.71 months (95% CI 9.37-16.05 months); test for differences between pNETs and epNETs (x12 = .35, p = .55). With regards to common grade 3/4 adverse events , patients who received anti-VEGF RTKIs were more likely to experience hypertension (IRR 3.04, 95% CI 1.63-5.65) and proteinuria (IRR 5.79, 95% CI 1.09-30.74) in comparison to those who received control.

CONCLUSIONS

Anti-VEGF RTKIs demonstrate anti-tumour effect in both pNETs and epNETs, supporting their development in both populations. These agents also appear to be safe in patients with NETs.

90Y/177Lu-DOTATOC: From Preclinical Studies to Application in Humans

The PRRT (Peptide Receptor Radionuclide Therapy) is a promising modality treatment for patients with inoperable or metastatic neuroendocrine tumors (NETs). Progression-free survival (PFS) and overall survival (OS) of these patients are favorably comparable with standard therapies. The protagonist in this type of therapy is a somatostatin-modified peptide fragment ([Tyr3] octreotide), equipped with a specific chelating system (DOTA) capable of creating a stable bond with β-emitting radionuclides, such as yttrium-90 and lutetium-177. In this review, covering twenty five years of literature, we describe the characteristics and performances of the two most used therapeutic radiopharmaceuticals for the NETs radio-treatment: [⁹⁰Y]Y-DOTATOC and [¹⁷⁷Lu]Lu-DOTATOC taking this opportunity to retrace the most significant results that have determined their success, promoting them from preclinical studies to application in humans.

Grading of pancreatic neuroendocrine neoplasms using pharmacokinetic parameters derived from dynamic contrast-enhanced MRI

The present study aimed to evaluate the diagnostic efficacy of pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in prospective evaluation of pancreatic neuroendocrine neoplasms (pNENs) grading. A total of 25 histologically proven patients with pNENs (30 lesions in total) who underwent DCE-MRI were enrolled. Lesions were divided into G1, G2 neuroendocrine tumor (NET) and G3 NET/neuroendocrine carcinoma (NEC) groups based on their histological findings according to 2017 World Health Organization Neuroendocrine Tumor Classification Guideline. In addition, the same numbers of tumor-free regions were selected using as normal control group. For each group, pharmacokinetic DCE parameters: volume transfer constant (K^trans); contrast transfer rate constant (k_ep); extravascular extracellular space volume fraction (v_e); and plasma volume fraction (v_p) were calculated with Extended Tofts Linear model. Receiver operator characteristics analysis was conducted to assess the diagnostic efficacy of these parameters in pNENs grading. There were significant differences of K^trans, k_ep, v_e and v_p between tumor-free areas and G1, G2 NET (P<0.001). The K^trans and k_ep of G1 NET were significantly lower compared with those of G2 ones (P<0.005). The area under the curve of K^trans and k_ep in differentiating G2 from G1 NET were 0.767 and 0.846, respectively. When K^trans was >0.667 and k_ep >1.644, the sensitivity of diagnosing G2 NET was the lowest (53.85%), but the specificity was the highest (93.75%). When K^trans was >0.667 or k_ep >1.644, the sensitivity of diagnosing G2 NET was 92.31%, but the specificity was 75.00%. Pharmacokinetic parameters of DCE-MRI, particularly the quantitative values of K^trans and k_ep, are helpful for differentiating G2 NET from G1 ones.

Anticancer Efficacy of Self-Nanoemulsifying Drug Delivery System of Sunitinib Malate

Sunitinib malate (SM) is reported as a weakly soluble drug in water due to its poor dissolution rate and oral bioavailability. Hence, in the current study, various "self-nanoemulsifying drug delivery systems (SNEDDS)" of SM were prepared, characterized and evaluated for the enhancement of its in vitro dissolution rate and anticancer efficacy. On the basis of solubilization potential of SM in various excipients, "Lauroglycol-90 (oil), Triton-X100 (surfactant) and Transcutol-P (cosurfactant)" were selected for the preparation of SM SNEDDS. SM-loaded SNEDDS were developed by spontaneous emulsification method, characterized and evaluated for "thermodynamic stability, self-nanoemulsification efficiency, droplet size, polydispersity index (PDI), zeta potential (ZP), surface morphology, refractive index (RI), the percent of transmittance (% T) and drug release profile." In vitro dissolution rate of SM was significantly enhanced from an optimized SNEDDS in comparison with SM suspension. The optimized SNEDDS of SM with droplet size of 42.3 nm, PDI value of 0.174, ZP value of -36.4 mV, RI value of 1.339, % T value of 97.3%, and drug release profile of 95.4% (after 24 h via dialysis membrane) was selected for in vitro anticancer efficacy in human colon cancer cells (HT-29) by MTT assay. MTT assay indicated significant anticancer efficacy of optimized SM SNEDDS against HT-29 cells in comparison with free SM. The results of this study showed the great potential of SNEDDS in the enhancement of in vitro dissolution rate and anticancer efficacy of poorly soluble drug such as SM.

Transcriptional alterations in hereditary and sporadic nonfunctioning pancreatic neuroendocrine tumors according to genotype

BACKGROUND

Nonfunctioning pancreatic neuroendocrine tumors (NFPanNETs) may be sporadic or inherited because of germline mutations associated with von Hippel-Lindau disease (VHL) or multiple endocrine neoplasia type 1 (MEN1). The clinical behavior of NFPanNETs is difficult to predict, even in tumors of the same stage and grade. The authors analyzed genotype-specific patterns of transcriptional messenger RNA (mRNA) levels of NFPanNETs to understand the molecular features that determine PanNET phenotype.

METHODS

Thirty-two samples were included for genome-wide mRNA gene expression analysis (9 VHL-associated, 10 MEN1-associated, and 9 sporadic NFPanNETs and 4 purified normal islet cell [NIC] samples). Validation of genes was performed by real-time polymerase chain reaction analysis and immunohistochemistry. Gene expression profiles were analyzed by tumor genotype, and pathway analysis was curated.

RESULTS

Consensus clustering of mRNA expression revealed separate clustering of NICs, VHL-associated NFPanNETs, and MEN1-associated NFPanNETs; whereas some sporadic tumors clustered with MEN1. Four of 5 MEN1-like sporadic PanNET subtypes had loss of heterozygosity at the MEN1 gene locus. Pathway analysis demonstrated subtype-specific pathway activation, comprising angiogenesis and immune response in VHL; neuronal development in MEN1; protein ubiquitination in the new MEN1/sporadic subtype; and cytokinesis and cilium/microtubule development in sporadic NFPanNETs. Among many genes, platelet-derived growth factor receptor β (PDGFRB), lymphoid enhancer-binding factor-1 (Lef-1), cyclin-dependent kinase 4 (CDK4), and CDK6 were upregulated in VHL or MEN1 NFPanNETs, providing potential subtype-specific treatment targets.

CONCLUSIONS

Distinct mRNA expression patterns were identified in sporadic-associated, VHL-associated, and MEN1-associated NFPanNETs. The current results uncover new pathways involved in NFPanNETs that are subtype-specific and provide potential new diagnostic or therapeutic targets based on tumor subtype. Cancer 2018;124:636-47. © 2017 American Cancer Society.

Pancreatic Neuroendocrine Neoplasms: Basic Biology, Current Treatment Strategies and Prospects for the Future

Pancreatic neuroendocrine neoplasms (pNENs) are rare tumors accounting for only 1%–2% of all pancreatic tumors. pNENs are pathologically heterogeneous and are categorized into three groups (neuroendocrine tumor: NET G1, NET G2; and neuroendocrine carcinoma: NEC) on the basis of the Ki-67 proliferation index and the mitotic count according to the 2010 World Health Organization (WHO) classification of gastroenteropancreatic NENs. NEC in this classification includes both histologically well-differentiated and poorly differentiated subtypes, and modification of the WHO 2010 classification is under discussion based on genetic and clinical data. Genomic analysis has revealed NETs G1/G2 have genetic alterations in chromatin remodeling genes such as MEN1, DAXX and ATRX, whereas NECs have an inactivation of TP53 and RB1, and these data suggest that different treatment approaches would be required for NET G1/G2 and NEC. While there are promising molecular targeted drugs, such as everolimus or sunitinib, for advanced NET G1/G2, treatment stratification based on appropriate predictive and prognostic biomarkers is becoming an important issue. The clinical outcome of NEC is still dismal, and a more detailed understanding of the genetic background together with preclinical studies to develop new agents, including those already under investigation for small cell lung cancer (SCLC), will be needed to improve the prognosis.

Increased Activity of the Immunoregulatory Enzyme Indoleamine-2,3-Dioxygenase with Consecutive Tryptophan Depletion Predicts Death in Patients with Neuroendocrine Neoplasia

BACKGROUND/AIMS

Data from a considerable number of malignancies demonstrate that depletion of the essential amino acid tryptophan via induction of the immunoregulatory enzyme indoleamine-2,3-dioxygenase (IDO) serves as an important tumour escape strategy and is of prognostic importance. Here we investigate the predictive value of the activity of IDO as well as levels of tryptophan and respective downstream catabolites in a large cohort of patients with neuroendocrine neoplasms (NEN).

METHODS

142 consecutive Caucasian patients (62 male, aged 60.3 ± 11.9 years) with histologically confirmed NEN were systematically analysed in a retrospective blinded end point analysis. Patients were followed up for a mean period of about 3.9 ± 1.9 years. Clinical outcome, levels of established biomarkers, and tryptophan degradation markers (assessed using tandem mass spectrometry) including estimated IDO activity were recorded. Cox proportional hazards regression models were performed for the assessment of prognostic power.

RESULTS

We found that baseline tryptophan levels were significantly lower and IDO activity was significantly increased in non-survivors. The risk for death inclined stepwise and was highest in patients in the upper tertile of IDO activity. Cox proportional regression models identified IDO activity as an independent predictor of death.

CONCLUSIONS

In this retrospective analysis, we observed that baseline activity of the immunoregulatory enzyme IDO was significantly increased in non-survivors. IDO activity was identified as an independent predictor of death in this cohort of NEN patients. Whether IDO activity or tryptophan depletion serves to guide future therapeutic interventions in NEN remains to be established.

The pivotal role of mammalian target of rapamycin inhibition in the treatment of patients with neuroendocrine tumors

Significant advances have been made toward understanding the biology of neuroendocrine tumors (NET) in terms of defining prognosis and improving clinical management; however, many unmet needs remain. The treatment landscape for NET has evolved, with the approval of the targeted agents everolimus and sunitinib for the treatment of advanced pancreatic NET in 2011 followed by the approval of everolimus for the treatment of advanced nonfunctional gastrointestinal and lung NET in 2016. Mammalian target of rapamycin (mTOR) and components of the mTOR pathway play pivotal roles in NET pathogenesis. Effects of the mTOR inhibitor everolimus have been well documented in preclinical and clinical studies, both as monotherapy and combination therapy. mTOR inhibition as backbone therapy within the NET treatment landscape is a focus of continuing research, which includes evaluation of the growing armamentarium of approved and investigational agents as potential combination partners. Data evaluating the clinical benefits of agents targeting mTOR and related pathways (alone and in combination) in the treatment of patients with NET continue to increase. Many of the findings to date are encouraging.

Identification of immunotherapeutic targets by genomic profiling of rectal NET metastases

Neuroendocrine tumors (NETs) of the gastrointestinal tract are a rare and heterogeneous group of neoplasms with unique tumor biology and clinical management issues. While surgery is the only curative treatment option in patients with early stage NETs, the optimal management strategy for patients with advanced metastatic NETs is unknown. Based on the tremendous success of immunotherapeutic approaches, we sought to investigate such approaches in a case of metastatic rectal NET. Here, we apply an integrative approach using various computational and experimental methods to explore several aspects of the tumor-host immune interactions for immunotherapeutic options. Sequencing of six different liver metastases revealed a quite homogenous set of mutations, and further analysis of these mutations for immunogenicity revealed few neo-epitopes with pre-existing T cell reactivity, which can be used in therapeutic vaccines. Staining for immunomodulatory proteins and cytokine profiling showed that the immune setting is surprisingly different, when compared to liver metastases of colorectal cancer for instance. Taken together, our results highlight the broad range and complexity of tumor-host immune interaction and underline the value of an integrative approach.

Molecular classification of gastric cancer: Towards a pathway-driven targeted therapy

Gastric cancer (GC) is the third leading cause of cancer mortality worldwide. Although surgical resection is a potentially curative approach for localized cases of GC, most cases of GC are diagnosed in an advanced, non-curable stage and the response to traditional chemotherapy is limited. Fortunately, recent advances in our understanding of the molecular mechanisms that mediate GC hold great promise for the development of more effective treatment strategies. In this review, an overview of the morphological classification, current treatment approaches, and molecular alterations that have been characterized for GC are provided. In particular, the most recent molecular classification of GC and alterations identified in relevant signaling pathways, including ErbB, VEGF, PI3K/AKT/mTOR, and HGF/MET signaling pathways, are described, as well as inhibitors of these pathways. An overview of the completed and active clinical trials related to these signaling pathways are also summarized. Finally, insights regarding emerging stem cell pathways are described, and may provide additional novel markers for the development of therapeutic agents against GC. The development of more effective agents and the identification of biomarkers that can be used for the diagnosis, prognosis, and individualized therapy for GC patients, have the potential to improve the efficacy, safety, and cost-effectiveness for GC treatments.

Histological features of mixed neuroendocrine carcinoma and hepatocellular carcinoma in the liver: a case report and literature review

Primary hepatic neuroendocrine carcinoma (NEC) is rare, and its origin, clinical features, diagnosis and treatment have not been clarified. Primary mixed NEC and hepatocellular carcinoma (HCC) is even rarer and is divided into either combined type or collision type. We report a patient with the combined type of mixed NEC and HCC. A 72-year-old male was diagnosed with HCC and underwent hepatectomy because of the presence of two tumors in his liver. Histological examination demonstrated that one of the tumors had both NEC and HCC components. The transitional zone was noted in the immunohistological examination, and the tumor was determined to be the combined type of primary mixed NEC and HCC. This was the first description of an HCC component being found in an NEC-dominant area in a primary mixed NEC and HCC tumor. Three weeks after hepatectomy, an abdominal computed tomography scan showed extensive regional and para-aortic lymphadenopathy, and early relapse was suspected in the patient. The patient died 3 months after the operation despite treatment with combination chemotherapy. This report describes an unfavorable case and summarizes all the primary mixed NEC and HCC tumor cases that have been previously reported.

New horizons for targeted treatment of neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare and heterogeneous tumors and there is a paucity of randomized clinical trials evaluating the different therapeutic strategies. Over recent years, some important molecular aspects have been investigated and multiple targeted therapies are currently available. One of the most promising targets for the therapy of NETs are the mTOR and angiogenic growth factor receptors. The advent of the inhibitors of the mTOR pathway, tyrosine kinase inhibitors and of somatostatin analogs have shown their efficacy in randomized clinical trials in terms of implementing clinical hormone-induced syndromes and progression-free survival of advanced NETs. This article summarizes the standard therapies and new perspectives in NET's treatment, which remains still very heterogeneous and little known entity.

Challenges in the Diagnosis and Management of Well-Differentiated Neuroendocrine Tumors of the Lung (Typical and Atypical Carcinoid): Current Status and Future Considerations

Neuroendocrine tumors (NET) of the lung represent approximately 25% of all primary lung tumors and can be classified as low grade (typical carcinoids), intermediate grade (atypical carcinoids), or high grade (large cell neuroendocrine carcinoma or small cell lung carcinoma). Low- and intermediate-grade lung NET are increasingly recognized as biologically distinct from high-grade lung NET based on clinical behavior and underlying molecular abnormalities. This review summarizes current knowledge and challenges in the diagnosis and management of low- and intermediate-grade lung NET. Accurate histopathologic classification of lung NET is critical to determining appropriate treatment options but can be challenging even for experts. For low- and intermediate-grade lung NET, surgery remains the mainstay of treatment for localized disease. Although no standard systemic therapy has been established for the treatment of advanced, unresectable disease, a number of promising treatment options are emerging, including somatostatin analogs, temozolomide-based chemotherapy, targeted therapy with mammalian target of rapamycin or vascular endothelial growth factor inhibitors, and peptide receptor radionuclide therapy. Given the difficulty in accurately diagnosing these tumors, and the paucity of data supporting establishment of standard systemic therapy options, management of patients within the setting of a multidisciplinary team, including specialists with expertise in NET, is recommended. Ongoing and future clinical trials hopefully will provide stronger evidence to support treatment recommendations for low- and intermediate-grade lung NET.

The JAK/STAT signaling cascade in gastric carcinoma (Review)

Gastric carcinoma remains one of the most prevalent forms of cancer worldwide, despite the decline in incidence rates, increased awareness of the disease and advancement in treatment strategies. Helicobacter pylori infection, dietary factors, lifestyle influences and various genetic aberrations have been shown to contribute to the development and progression of gastric cancer. Recent studies on the genomic landscape of gastric adenocarcinoma have identified several key signaling molecules, including epidermal growth factor receptor family (ErbB) members, vascular endothelial growth factor receptor family (VEGFR) members and PI3K/Akt/mTOR pathway components, that have been implicated in the molecular pathogenesis of gastric cancers. However, clinical trials with compounds that target these molecules have failed to show a significant improvement in overall survival rates when supplemented with conventional therapies. Therefore, it is essential to identify effective prognostic and/or diagnostic biomarkers and develop molecular targeted therapies. The JAK/STAT cascade is a principal signal transduction pathway in cytokine and growth factor signaling, regulating various cellular processes such as cell proliferation, differentiation, migration and survival. Numerous in vivo and in vitro studies have shown that dysregulated JAK/STAT signaling is a driving force in the pathogenesis of various solid cancers as well as hematopoietic malignancies. Hence, a large number of preclinical and clinical studies of drugs targeting this pathway are currently underway. Notably, aberrant JAK/STAT signaling has also been implicated in gastric cancers. In this review, we focus on the ongoing research on the JAK/STAT cascade in gastric carcinoma and discuss the therapeutic potential of targeting JAK/STAT signaling for the treatment of gastric cancer.

Octreotide long-acting repeatable among elderly patients with neuroendocrine tumors: a survival analysis of SEER-Medicare data

BACKGROUND

Octreotide long-acting repeatable (LAR) is approved in the United States for the management of carcinoid syndromes among patients with neuroendocrine tumors (NET). The objective of our study is to evaluate the impact of octreotide LAR on overall survival (OS), as it has not been established.

METHODS

NET patients of 65 years and older diagnosed between January 1999 and December 2009 were identified from the SEER-Medicare database. We compared the OS of NET patients who started octreotide LAR within 12 months of diagnosis with those who did not receive it during the same period. We conducted Kaplan-Meier estimations and Cox proportional hazard models to examine the association between octreotide LAR and OS.

RESULTS

Among 1,176 distant stage patients, 233 (20%) received octreotide LAR within 12 months of diagnosis, compared with 2% (96 in 5,764) of local/regional stage patients. Median OS for patients who started octreotide LAR within 12 months was 35.22 months [95% confidence interval (CI), 27.96-47.77], longer than those who did not receive it (19.15 months; 95% CI, 16.36-22.80; P < 0.0001). Multivariate analysis showed that octreotide LAR was associated with significant survival improvement for distant stage patients (HR, 0.68; P < 0.001) and in the subgroups with (HR, 0.65; P, 0.003) and without (HR, 0.55; P, 0.002) carcinoid syndrome. No survival benefit was found among local/regional stage patients.

CONCLUSION

This population-based study suggests potential survival benefits of octreotide LAR among elderly distant stage NET patients, both with or without carcinoid syndrome.

IMPACT

The study provides population-based evidence of a positive association between octreotide LAR and overall survival among elderly distant stage NET patients.

Mutation-targeted therapy with sunitinib or everolimus in patients with advanced low-grade or intermediate-grade neuroendocrine tumours of the gastrointestinal tract and pancreas with or without cytoreductive surgery: protocol for a phase II clinical trial

INTRODUCTION

Finding the optimal management strategy for patients with advanced, metastatic neuroendocrine tumours (NETs) of the gastrointestinal tract and pancreas is a work in progress. Sunitinib and everolimus are currently approved for the treatment of progressive, unresectable, locally advanced or metastatic low-grade or intermediate-grade pancreatic NETs. However, mutation-targeted therapy with sunitinib or everolimus has not been studied in this patient population.

METHODS AND ANALYSIS

This prospective, open-label phase II clinical trial was designed to determine if mutation-targeting therapy with sunitinib or everolimus for patients with advanced low-grade or intermediate-grade NETs is more effective than historically expected results with progression-free survival (PFS) as the primary end point. Patients ≥18 years of age with progressive, low-grade or intermediate-grade locally advanced or metastatic NETs are eligible for this study. Patients will undergo tumour biopsy (if they are not a surgical candidate) for tumour genotyping. Patients will be assigned to sunitininb or everolimus based on somatic/germline mutations profile. Patients who have disease progression on either sunitinib or everolimus will crossover to the other drug. Treatment will continue until disease progression, unacceptable toxicity, or consent to withdrawal. Using the proposed criteria, 44 patients will be accrued within each treatment group during a 48-month period (a total of 88 patients for the 2 treatments), and followed for up to an additional 12 months (a total of 60 months from entry of the first patient) to achieve 80% power in order to test whether there is an improvement in PFS compared to historically expected results, with a 0.10 α level one-sided significance test.

ETHICS AND DISSEMINATION

The study protocol was approved by the institutional review board of the National Cancer Institute (NCI-IRB Number 15C0040; iRIS Reference Number 339636). The results will be published in a peer-reviewed journal and shared with the worldwide medical community.

TRIAL REGISTRATION NUMBER

NCT02315625.

Management of pancreatic neuroendocrine tumors

Abstract: 

Despite the rarity of the disease, there has been significant recent progress in the management of pancreatic neuroendocrine tumors (PNETs). Arterial phase imaging and somatostatin scintigraphy are important parts of the diagnostic and staging work-up of PNETs. The slow growth rate of PNETs can make observation a reasonable initial option in low volume asymptomatic disease or allow debulking surgery in selected patients with advanced disease. Somatostatin analogs, angiogenesis and mTOR inhibitors have proven benefit for PNET patients in randomized trials while retrospective and single-arm trials using chemotherapy or peptide receptor radiation therapy also appear promising. This review summarizes key aspects in the management of PNETs with emphasis on the most recent advances in systemic therapy.

Neuroendocrine neoplasms of the pancreas at dynamic enhanced CT: comparison between grade 3 neuroendocrine carcinoma and grade 1/2 neuroendocrine tumour

OBJECTIVES

To identify the CT features in differentiating grade 3 neuroendocrine carcinomas from grade 1/2 neuroendocrine tumours.

METHODS

This study included 161 patients with surgically confirmed pancreatic neuroendocrine neoplasms. Pathology slides were reviewed to determine the tumour grade. CT image analysis included size, pattern, calcification, margin, pancreatic duct dilatation, bile duct dilatation, vascular invasion, arterial enhancement ratio, and portal enhancement ratio. We used 2 cm, 3 cm, and 4 cm as cutoff values of tumour size and 0.9 and 1.1 of enhancement ratio to determine the sensitivity and specificity.

RESULTS

Pathology analysis identified 167 lesions in 161 patients. 154 lesions (92 %) were grade 1/2 and 13 (8 %) were grade 3. Portal enhancement ratio (< 1.1) showed high sensitivity and specificity 92.3 % and 80.5 %, respectively in differentiating grade 3 from grade 1/2. It showed the highest odds ratio (49.60), followed by poorly defined margin, size (> 3 cm), bile duct dilatation, and vascular invasion. When at least two of these five criteria were used in combination, the sensitivity and specificity for diagnosing grade 3 were 92.3 % (12/13) and 87.7 % (135/154), respectively.

CONCLUSIONS

By using specific CT findings, grade 3 can be differentiated from grade 1/2 with a high diagnostic accuracy leading to an appropriate imaging staging.

KEY POINTS

• Neuroendocrine carcinomas should be differentiated from neuroendocrine tumours. • Neuroendocrine carcinomas can be differentiated from neuroendocrine tumours on dynamic CT. • Neuroendocrine carcinomas show iso- or hypo-enhancement on portal venous phase CT.

Primary hepatic neuroendocrine carcinoma with a cholangiocellular carcinoma component in one nodule

Primary neuroendocrine carcinomas (NECs) in the liver are very rare; however, several reports have described cases of a primary hepatic NEC combined with a hepatocellular carcinoma (HCC). We present the first report of a primary hepatic NEC with a cholangiocellular carcinoma (CCC) component in one nodule in a patient with a metachronous liver HCC. A 73-year old man who had received partial hepatectomy surgery because of a primary HCC and a primary CCC two years prior was diagnosed with a primary hepatic NEC after surgical treatment. Histological analysis of the resected tumor revealed that the tumor consisted of a predominant NEC area with a partial CCC component in one nodule and that the NEC cells were negative for markers of pancreatic NEC. Neoplastic cells in both the NEC and CCC component focally expressed CD44, a representative marker for cancer-initiating cells, and the CD44-positive cells in the NEC component were seen in the vicinity of those in the CCC component of one nodule. This case report provides suggestive information for the origin of primary hepatic NECs.

Targeted therapy for gastric cancer: molecular pathways and ongoing investigations

Gastric cancer is currently the second leading cause of worldwide cancer mortality. Ongoing collaborative sequencing efforts have highlighted recurrent somatic genomic aberrations in gastric cancer, however, despite advances in characterizing the genomic landscape, there have been few advances in patient outcomes. Prognosis remains poor with a median overall survival of 12 months for advanced disease. The improved survival with trastuzumab, and more recently ramucirumab, underscore the promise of targeted and biologic therapies and the importance of molecular tumor characterization in gastric cancer. Here we review the most frequent actionable alterations in gastric cancer and highlight ongoing clinical investigations attempting to translate biologic understanding into improved clinical outcomes.

Surgery for giant primary neuroendocrine carcinoma of the liver

Liver resection for primary hepatic neuroendocrine carcinoma (phNEC) has only scarcely been reported in the literature. We herein report on a 19-year-old female with a solitary 27 × 13-cm-big phNEC, which was initially considered as hemangioma. An extended right hepatectomy (segments V-VIII, partially IVa) was performed. Resection margins were free of tumor (R0 resection). Ki67 expression was 35%. Postoperative course was uneventful, and the patient was discharged on the seventh postoperative day. Two years after surgery, the patient remains disease-free and in good general condition. Large series and longer follow-up studies are required for the better understanding on this rare tumor entity.

p53 suppresses carcinoma progression by inhibiting mTOR pathway activation

Genetic alterations in human cancers and murine models indicate that Rb and p53 have critical tumor suppressive functions in retinoblastoma, a tumor of neural origin, and neuroendocrine tumors including small cell lung cancer and medullary thyroid cancer (MTC). Rb inactivation is the initiating lesion in retinoblastoma and current models propose that induction of apoptosis is a key p53 tumor suppressive function. Genetic studies in mice, however, indicate that other undefined p53 tumor suppressive functions are operative in vivo. How p53 loss cooperates with Rb inactivation to promote carcinogenesis is also not fully understood. In the current study, genetically engineered mice were generated to determine the role of Rb and p53 in MTC pathogenesis and test the hypothesis that p53 suppresses carcinogenesis by inhibiting mTOR signaling. Conditional Rb ablation resulted in thyroid tumors mimicking human MTC, and additional p53 loss led to rapid tumor progression. p53 suppressed tumorigenesis by inhibiting cell cycle progression, but did not induce apoptosis. On the contrary, p53 loss led to increased apoptosis that had to be overcome for tumor progression. mTOR activity was markedly increased in p53 deficient tumors and rapamycin treatment suppressed tumor cell growth identifying mTOR inhibition as a critical p53 tumor suppressive function. Rapamycin treatment did not result in AKT/MAPK activation providing evidence that this feedback mechanism operative in other cancers is not a general response to mTORC1 inhibition. Together, these studies provide mechanistic links between genetic alterations and aberrant signaling pathways critical in carcinogenesis, and identify essential Rb and p53 tumor suppressive functions in vivo.

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

OBJECTIVE

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

CONCLUSION

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

[Drug therapy for neuroendocrine tumours]

The author aims to review the established medical treatment options of neuroendocrine tumours, which have expanded greatly in recent years and present the most important aspects to be considered in planning patients' management. Medical treatment is usually considered in advanced stages of these tumours, as well as in cases of hormone overproduction. Somatostatin analogues have been known to be effective in alleviating hormone excess syndromes, especially carcinoid syndrome for the past 25 years. There is a convincing evidence that the somatostatin analogue octreotide is useful as an antitumor agent, at least in well-differentiated small intestinal neuroendocrine tumours and probably also in those of pancreatic origin. Interferons may be also used and the indications for their use may be almost the same. Optimal patient selection is mandatory for the use of cytotoxic chemotherapy. Streptozotocin- and, recently, temozolomide-based chemotherapies should be considered in progressive phases of well differentiated (G1/G2) pancreatic neuroendocrine tumours. A cisplatin-etoposide combination is the first choice for the treatment of G3 neuroendocrine carcinomas of any origin. Recently, the mammalian target of rapamycin inhibitor everolimus and the combined tyrosine kinase inhibitor sunitinib were registered for the treatment of G1/G2 pancreatic neuroendocrine tumours. The most recent drug treatment recommendations and therapeutic algorithms to improve systemic therapy in patients with neuroendocrine tumours are summarized and novel drug candidates with particular potential for future management of these tumours are outlined.

Direct cytosolic delivery of polar cargo to cells by spontaneous membrane-translocating peptides

Direct cellular entry of potentially useful polar compounds into cells is prevented by the hydrophobic barrier of the membrane. Toward circumventing this barrier, we used high throughput screening to identify a family of peptides that carry membrane-impermeant cargos across synthetic membranes. Here we characterize the plasma membrane translocation of these peptides with polar cargos under a variety of conditions. The spontaneous membrane-translocating peptides (SMTPs) delivered the zwitterionic, membrane-impermeant dye tetramethylrhodamine (TAMRA) into cells even when the conditions were not permissive for endocytosis. They also delivered the larger, anionic membrane-impermeant dye Alexa Fluor 546 but did not deliver a quantum dot nanoparticle. Under all conditions, the SMTP-cargo filled the cytoplasm with a diffuse, non-punctate fluorescence that was partially excluded from the nucleus. D-amino acid peptides behaved identically in vitro, ruling out proteolysis as an important factor in the diffuse cellular distribution. Thus, cytosolic delivery of SMTP-cargo conjugates is dominated by direct membrane translocation. This is in sharp contrast to Arg9-TAMRA, a representative highly cationic, cell-penetrating peptide, which entered cells only when endocytosis was permitted. Arg9-TAMRA triggered large scale endocytosis and did not appreciably escape the endosomal compartments in the 1-h timescales we studied. When injected into mice, SMTP-TAMRA conjugates were found in many tissues even after 2 h. Unconjugated TAMRA was rapidly cleared and did not become systemically distributed. SMTPs are a platform that could improve delivery of many polar compounds to cells, in the laboratory or in the clinic, including those that would otherwise be rejected as drugs because they are membrane-impermeant.

mTOR, p70S6K, AKT, and ERK1/2 levels predict sensitivity to mTOR and PI3K/mTOR inhibitors in human bronchial carcinoids

Bronchial carcinoids (BCs) are rare neuroendocrine tumors that are still orphans of medical treatment. Human BC primary cultures may display resistance to everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), in terms of cell viability reduction. Our aim was to assess whether the novel dual phosphatidylinositol 3-kinase (PI3K)/mTOR inhibitor NVP-BEZ235 is effective in everolimus-resistant human BC tissues and cell lines. In addition, we searched for possible markers of the efficacy of mTOR inhibitors that may help in identifying the patients who may benefit from treatment with mTOR inhibitors, sparing them from ineffective therapy. We found that NVP-BEZ235 is twice as potent as everolimus in reducing cell viability and activating apoptosis in human BC tissues that display sensitivity to mTOR inhibitors, but is not effective in everolimus-resistant BC tissues and cell lines that bypass cyclin D1 downregulation and escape G0/G1 blockade. Rebound AKT activation was not observed in response to treatment with either mTOR inhibitor in the 'resistant' BC cells. In addition to total mTOR levels, putative markers of the sensitivity of BCs to mTOR inhibitors are represented by AKT, p70S6K (RPS6KB2), and ERK1/2 (MAPK3/1) protein levels. Finally, we validated these markers in an independent BC group. These data indicate that the dual PI3K/mTOR inhibitor NVP-BEZ235 is more potent than everolimus in reducing the proliferation of human BC cells. 'Resistant' cells display lower levels of mTOR, p70S6K, AKT, and ERK1/2, indicating that these proteins may be useful as predictive markers of resistance to mTOR and PI3K/mTOR inhibitors in human BCs.

The role of mechanistic target of rapamycin (mTOR) complexes signaling in the immune responses

The mechanistic Target of Rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase which is a member of the PI3K related kinase (PIKK) family. mTOR emerged as a central node in cellular metabolism, cell growth, and differentiation, as well as cancer metabolism. mTOR senses the nutrients, energy, insulin, growth factors, and environmental cues and transmits signals to downstream targets to effectuate the cellular and metabolic response. Recently, mTOR was also implicated in the regulation of both the innate and adaptive immune responses. This paper will summarize the current knowledge of mTOR, as related to the immune microenvironment and immune responses.

Evaluation of the WHO 2010 grading and AJCC/UICC staging systems in prognostic behavior of intestinal neuroendocrine tumors

Background

The increasing incidence and heterogeneous behavior of intestinal neuroendocrine tumors (iNETs) pose a clinicopathological challenge. Our goal was to decribe the prognostic value of the new WHO 2010 grading and the AJCC/UICC TNM staging systems for iNETs. Moreover, outcomes of patients treated with somatostatin analogs were assessed.

Methods

We collected epidemiological and clinicopathological data from 93 patients with histologically proven iNETs including progression and survival outcomes. The WHO 2010 grading and the AJCC/UICC TNM staging systems were applied for all cases. RECIST criteria were used to define progression. Kaplan-Meier analyses for progression free survival (PFS) and overall survival (OS) were performed.

Results

Mean follow-up was 58.6 months (4–213 months). WHO 2010 grading yielded PFS and disease-specific OS of 125.0 and 165.8 months for grade 1 (G1), 100.0 and 144.2 months for G2 and 15.0 and 15.8 months for G3 tumors (p = 0.004 and p = 0.001). Using AJCC staging, patients with stage I and II tumors had no progression and no deaths. Stage III and IV patients demonstrated PFS of 138.4 and 84.7 months (p = 0.003) and disease-specific OS of 210.0 and 112.8 months (p = 0.017). AJCC staging also provided informative PFS (91.2 vs. 50.0 months, p = 0.004) and OS (112.3 vs. 80.0 months, p = 0.005) measures with somatostatin analog use in stage IV patients.

Conclusion

Our findings underscore the complementarity of WHO 2010 and AJCC classifications in providing better estimates of iNETS disease outcomes and extend the evidence for somatostatin analog benefit in patients with metastatic disease.

Long-term management of a patient with well-differentiated pulmonary neuroendocrine carcinoma: a case report

Pulmonary neuroendocrine tumors (NET) are rare, and very few published reports have described the long-term treatment of patients with this disease. Current treatment options for patients with metastatic well-differentiated pulmonary NET are limited. This case report details the long-term treatment of a 62-year-old female patient with well-differentiated pulmonary NET and multiple liver metastases. The heavily pretreated patient achieved radiographic stability in measurable disease, improvement in nonmeasurable disease, and symptomatic improvement over 3 years while receiving the combination of everolimus and octreotide long-acting repeatable (LAR). Treatment was well tolerated without mucositis, rash, or pneumonitis. This case report suggests that the combination of everolimus and octreotide LAR may be a novel treatment option for heavily pretreated patients with metastatic well-differentiated pulmonary NET, but these findings require further analysis in clinical trials.

Medical treatment of neuroendocrine tumours

PURPOSE OF REVIEW

This review summarizes results of recent clinical trials regarding the treatment of advanced neuroendocrine tumours (NETs) and pancreatic NETs (PNETs).

RECENT FINDINGS

Most NETs occur sporadically in the lung and the gastrointestinal tract, and their prevalence has apparently increased over the last decades. Although curative treatment can be accomplished by surgery, for some NETs, most present in advanced stages and alternative, medical therapy is indicated. Recent randomized clinical treatment trials using somatostatin analogues in well differentiated midgut NET and therapies targeting the mammalian target of rapamycin (mTOR) signalling pathway and various tyrosine kinases provided evidence of improved progression-free survival. Treatment of functional PNETs with the mTOR inhibitor everolimus also showed reduction of peptide secretion relevant to the presenting clinical syndrome.

SUMMARY

Previous work regarding the molecular pathology of NETs identified mTOR and tyrosine kinase signalling pathways as relevant targets in the neuroendocrine tumour biology. Subsequently, recent randomized clinical trials targeting these pathways with inhibitor therapies have provided encouraging results demonstrating prolonged progression-free survival and improvement of secretion-related clinical syndromes.

Therapy of metastatic pancreatic neuroendocrine tumors (pNETs): recent insights and advances

Neuroendocrine tumors (NETs) [carcinoids, pancreatic neuroendocrine tumors (pNETs)] are becoming an increasing clinical problem because not only are they increasing in frequency, but they can frequently present with advanced disease that requires diagnostic and treatment approaches different from those used in the neoplasms that most physicians are used to seeing and treating. In the past few years there have been numerous advances in all aspects of NETs including: an understanding of their unique pathogenesis; specific classification systems developed which have prognostic value; novel methods of tumor localization developed; and novel treatment approaches described. In patients with advanced metastatic disease these include the use of newer chemotherapeutic approaches, an increased understanding of the role of surgery and cytoreductive methods, the development of methods for targeted delivery of cytotoxic agents, and the development of targeted medical therapies (everolimus, sunitinib) based on an increased understanding of the disease biology. Although pNETs and gastrointestinal NETs share many features, recent studies show they differ in pathogenesis and in many aspects of diagnosis and treatment, including their responsiveness to different therapies. Because of limited space, this review will be limited to the advances made in the management and treatment of patients with advanced metastatic pNETs over the past 5 years.