Biotherapies for GEP-NETs

Role of filamin A in the pathogenesis of neuroendocrine tumors and adrenal cancer

Cell cytoskeleton proteins are involved in tumor pathogenesis, progression and pharmacological resistance. Filamin A (FLNA) is a large actin-binding protein with both structural and scaffold functions implicated in a variety of cellular processes, including migration, cell adhesion, differentiation, proliferation and transcription. The role of FLNA in cancers has been studied in multiple types of tumors. FLNA plays a dual role in tumors, depending on its subcellular localization, post-translational modification (as phosphorylation at Ser2125) and interaction with binding partners. This review summarizes the experimental evidence showing the critical involvement of FLNA in the complex biology of endocrine tumors. Particularly, the role of FLNA in regulating expression and signaling of the main pharmacological targets in pituitary neuroendocrine tumors, pancreatic neuroendocrine tumors, pulmonary neuroendocrine tumors and adrenocortical carcinomas, with implications on responsiveness to currently used drugs in the treatment of these tumors, will be discussed.

Clinical efficacy of first and second series of peptide receptor radionuclide therapy in patients with neuroendocrine neoplasm: a cohort study

OBJECTIVES

Peptide receptor radionuclide therapy (PRRT) is an established treatment for metastatic neuroendocrine neoplasms (NEN). However, only limited data exists for the effect of multiple series of PRRT. The aim of this study was to investigate PFS and OS inNEN patients treated with multiple series of PRRT conforming to the ENETS treatment protocol.

METHODS

We included all patients with gastrointestinal (GI), pancreatic and bronchopulmonary (BP) NEN treated with PRRT from 2008 to 2018. We used Kaplan-Meier estimation to evaluate PFS and OS with subgroup analysis of primary tumor, Ki67-index, type of radioisotope and number of PRRT series.

RESULTS

133 patients (female/male 61/72) were included, median age 70 (interquartile range 64-76) years. GI-NEN comprised 62%, pancreatic 23% and BP 11%. Median Ki67-index was 5%. After first PRRTG1- and G2-tumors had PFS of 25 and 22 months, compared to 11 months in G3-NENs (p < .05) and PFS was longer in G1/G2 GI-NENs than BP-NEN (30vs. 12 months, p < .05). After retreatment with a second series of PRRT, the overall PFS (G1-G3) was 19 months, with G1- and G2-tumors having the highest PFS of 19 and 22 months, respectively. Overall, the GI and BP tumors had an OS of 54 and 51 months.

CONCLUSIONS

PRRT is an effective therapy with long-term PFS and OS, especially in G1 and G2 NENs, and with better prognosis in GI-NEN compared with BP-NENs. OS and PFS was shorter after the second series of PRRT compared with the first, however results were still encouraging.

Medical Treatment of Gastrointestinal Neuroendocrine Neoplasms

Neuroendocrine neoplasms (NENs) are rare tumours that arise mainly in the gastrointestinal or pulmonary system. Most NENs are well-differentiated and may obtain prolonged survival besides the presence of metastatic disease; however, a subset (poorly differentiated NENs) may display a truly aggressive behaviour exhibiting a poor prognosis. The recently developed classification systems along with advances in functional imaging have helped stratify patients to the administration of appropriate therapeutic options. Surgery is the mainstay of treatment of NENs, but in recent decades there has been a considerable evolution of medical treatments that are used for locally advanced or metastatic disease not amenable to surgical resection. Long acting somatostatin analogues are the main therapeutic modality for patients with functioning and well-differentiated low grade NENs exhibiting symptomatic control and mainly stabilisation of tumour growth. Other systemic treatments include chemotherapy, molecular targeted agents, interferon-α, peptide receptor radionuclide therapy (PRRT), and immunotherapy. In addition, new agents such as telotristat may be used for the control of symptoms of carcinoid syndrome. The choice and/or sequence of therapeutic agents should be individualized according to tumour origin and differentiation, disease burden, presence of clinical symptoms and patients' performance status in the context of a multidisciplinary approach. Recent advances in the molecular pathogenesis of NENs set the field for a more personalised treatment approach.

Endocrinological Toxicity Secondary to Treatment of Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs)

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are increasingly recognized, characterized by prolonged survival even with metastatic disease. Their medical treatment is complex involving various specialties, necessitating awareness of treatment-related adverse effects (AEs). As GEP-NENs express somatostatin receptors (SSTRs), long-acting somatostatin analogs (SSAs) that are used for secretory syndrome and tumor control may lead to altered glucose metabolism. Everolimus and sunitinib are molecular targeted agents that affect glucose and lipid metabolism and may induce hypothyroidism or hypocalcemia, respectively. Chemotherapeutic drugs can affect the reproductive system and water homeostasis, whereas immunotherapeutic agents can cause hypophysitis and thyroiditis or other immune-mediated disorders. Treatment with radiopeptides may temporarily lead to radiation-induced hormone disturbances. As drugs targeting GEP-NENs are increasingly introduced, recognition and management of endocrine-related AEs may improve compliance and the quality of life of these patients.

Current treatment strategies for patients with advanced gastroenteropancreatic neuroendocrine tumors (GEP-NETs)

Background

Neuroendocrine tumors (NETs) are rare neoplasms, with an estimated annual incidence of ~ 6.9/100,000. NETs arise throughout the body from cells of the diffuse endocrine system. More than half originate from endocrine cells of the gastrointestinal tract and the pancreas, thus being referred to as gastroenteropancreatic NETs (GEP NETs). The only treatment that offers a cure is surgery, however most patients are diagnosed with metastatic disease, and curative surgery is usually not an option.Since the majority of patients are not candidate for curative surgery, they can be offered long-term systemic treatment, for both symptomatic relief and tumor growth suppression. Evidence based treatment options include somatostatin analogues, everolimus (an mTOR inhibitor), sunitinib (a tyrosine kinase inhibitor), peptide receptor radionuclide therapy (PRRT), chemotherapy, etc., alone or combined with cytoreductive procedures (surgery or liver directed procedures). However, there is an increasing need for novel therapies. Other treatment options being investigated are immunotherapy and epigenetic assessment that may lead to more personalized interventions. Following first line therapy with somatostatin analogues, there is no clear information to date indicating a preferred treatment sequence, and therefore the treatment approach should be individualized based on each NET patient characteristics.

Conclusions

NET patients are increasingly diagnosed throughout the world, usually with metastatic disease and requiring systemic therapy. We believe that each patient should be therefore thoroughly evaluated and individually discussed by a multidisciplinary and dedicated NET-expert team, updated with all treatment options including ongoing clinical trials, and before selecting the proper treatment sequence.

Telotristat ethyl: a novel agent for the therapy of carcinoid syndrome diarrhea

Carcinoid syndrome (CS), characterized by diarrhea and flushing, is present in 20% of patients with neuroendocrine tumors at diagnosis and becomes more frequent with progression. The diarrhea of CS is caused mainly by tumoral secretion of serotonin. It may not be fully controlled by somatostatin analogs, the currently indicated drugs for symptomatic relief. Telotristat ethyl is a novel inhibitor of tryptophan hydroxylase, the rate-limiting enzyme in serotonin biosynthesis. Administration of the drug decreases diarrhea in patients with CS. Telotristat ethyl was approved in February 2017 (USA) and September 2017 (European Commission) for the treatment of CS diarrhea in adults inadequately controlled by somatostatin analog alone. This drug is expected to greatly improve the health and quality of life of patients with CS diarrhea.

Midgut neuroendocrine tumor presenting with acute intestinal ischemia

Neuroendocrine tumors represent a heterogeneous group of neoplasms that arise from neuroendocrine cells and secrete various peptides and bioamines. While gastrointestinal neuroendocrine tumors, commonly called carcinoids, account for about 2/3 of all neuroendocrine tumors, they are relatively rare. Small intestine neuroendocrine tumors originate from intestinal enterochromaffin cells and represent about 1/4 of small intestine neoplasms. They can be asymptomatic or cause nonspecific symptoms, which usually leads to a delayed diagnosis. Imaging modalities can aid diagnosis and surgery remains the mainstay of treatment. We present a case of a jejunal neuroendocrine tumor that caused nonspecific symptoms for about 1 year before manifesting with acute mesenteric ischemia. Abdominal X-rays revealed pneumatosis intestinalis and an abdominal ultrasound and computed tomography confirmed the diagnosis. The patient was submitted to segmental enterectomy. Histopathological study demonstrated a neuroendocrine tumor with perineural and arterial infiltration and lymph node metastasis. The postoperative course was uneventful and the patient denied any adjuvant treatment.

Update in the Therapy of Advanced Neuroendocrine Tumors

OPINION STATEMENT

Neuroendocrine tumors (NETs) are rare neoplasms, with an estimated annual incidence of ~ 6.9/100,000. NETs arise throughout the body from cells of the diffuse endocrine system. More than half originate from endocrine cells of the gastrointestinal tract and the pancreas, thus being referred to as gastroenteropancreatic NETs (GEP-NETs). The only treatment that offers a cure is surgery; however, most patients are diagnosed with metastatic disease, and curative surgery is usually not an option. These patients can be offered long-term systemic treatment, for both symptomatic relief and tumor growth suppression. Evidence-based treatment options include somatostatin analogs, everolimus (a mTOR inhibitor), sunitinib (a tyrosine kinase inhibitor), and peptide receptor radionuclide therapy, alone or combined with cytoreductive procedures (surgery or liver-directed procedures). Other treatment options being investigated are immunotherapy and epigenetic assessment that may lead to more personalized interventions. We believe that each patient should be thoroughly evaluated and their case discussed by a multidisciplinary team that is up-to-date with all treatment modalities including ongoing clinical trials, before selecting the proper treatment option.

Identification of human somatostatin receptor 2 domains involved in internalization and signaling in QGP-1 pancreatic neuroendocrine tumor cell line

Somatostatin exerts inhibitory effects on hormone secretion and cell proliferation via five receptor subtypes (SST1-SST5), whose internalization is regulated by β-arrestins. The receptor domains involved in these effects have been only partially elucidated. The aim of the study is to characterize the molecular mechanism and determinants responsible for somatostatin receptor 2 internalization and signaling in pancreatic neuroendocrine QGP-1 cell line, focusing on the third intracellular loop and carboxyl terminal domains. We demonstrated that in cells transfected with somatostatin receptor 2 third intracellular loop mutant, no differences in β-arrestins recruitment and receptor internalization were observed after somatostatin receptor 2 activation in comparison with cells bearing wild-type somatostatin receptor 2. Conversely, the truncated somatostatin receptor 2 failed to recruit β-arrestins and to internalize after somatostatin receptor 2 agonist (BIM23120) incubation. Moreover, the inhibitory effect of BIM23120 on cell proliferation, cyclin D1 expression, P-ERK1/2 levels, apoptosis and vascular endothelial growth factor secretion was completely lost in cells transfected with either third intracellular loop or carboxyl terminal mutants. In conclusion, we demonstrated that somatostatin receptor 2 internalization requires intact carboxyl terminal while the effects of SS on cell proliferation, angiogenesis and apoptosis mediated by somatostatin receptor 2 need the integrity of both third intracellular loop and carboxyl terminal.

Refractory carcinoid syndrome: a review of treatment options

Carcinoid syndrome (CSy) is a constellation of symptoms that may commonly present in patients with well differentiated neuroendocrine tumors (NETs), with somatostatin analogs (SSAs) being the first-line option for symptom management. However, symptomatic progression eventually occurs and in this scenario of a refractory CSy; several treatment options have been studied such as dose escalation of SSA, interferon and liver-directed therapies. Nevertheless, recent phase III trials have contributed to the understanding and management of this condition. We performed a comprehensive review of interventional studies examining refractory CSy to provide the evidence for current treatment options and propose a treatment sequence.

The treatment of hyperinsulinemic hypoglycaemia in adults: an update

BACKGROUND

Treatment of hyperinsulinemic hypoglycaemia (HH) is challenging due to the rarity of this condition and the difficulty of differential diagnosis. The aim of this article is to give an overview of the recent literature on the management of adult HH.

METHODS

A search for reviews, original articles, original case reports between 1995 and 2016 in PubMed using the following keywords: hyperinsulinemic hypoglycaemia, insulinoma, nesidioblastosis, gastric bypass, autoimmune hypoglycaemia, hyperinsulinism, treatment was performed.

RESULTS

One hundred and forty articles were selected and analysed focusing on the most recent treatments of HH.

CONCLUSIONS

New approaches to treatment of HH are available including mini-invasive surgical techniques and alternative local-regional ablative therapy for benign insulinoma and everolimus for malignant insulinoma. A correct differential diagnosis is of paramount importance to avoid unnecessary surgical operations and to implement the appropriate treatment mainly in the uncommon forms of HH, such as nesidioblastosis and autoimmune hypoglycaemia.

Filamin-A is required to mediate SST2 effects in pancreatic neuroendocrine tumours

Somatostatin receptor type 2 (SST2) is the main pharmacological target of somatostatin (SS) analogues widely used in patients with pancreatic neuroendocrine tumours (P-NETs), this treatment being ineffective in a subset of patients. Since it has been demonstrated that Filamin A (FLNA) is involved in mediating GPCR expression, membrane anchoring and signalling, we investigated the role of this cytoskeleton protein in SST2 expression and signalling, angiogenesis, cell adhesion and cell migration in human P-NETs and in QGP1 cell line. We demonstrated that FLNA silencing was not able to affect SST2 expression in P-NET cells in basal conditions. Conversely, a significant reduction in SST2 expression (-43 ± 21%, P < 0.05 vs untreated cells) was observed in FLNA silenced QGP1 cells after long term SST2 activation with BIM23120. Moreover, the inhibitory effect of BIM23120 on cyclin D1 expression (-46 ± 18%, P < 0.05 vs untreated cells), P-ERK1/2 levels (-42 ± 14%; P < 0.05 vs untreated cells), cAMP accumulation (-24 ± 3%, P < 0.05 vs untreated cells), VEGF expression (-31 ± 5%, P < 0.01 vs untreated cells) and in vitro release (-40 ± 24%, P < 0.05 vs untreated cells) was completely lost after FLNA silencing. Interestingly, BIM23120 promoted cell adhesion (+86 ± 45%, P < 0.05 vs untreated cells) and inhibited cell migration (-24 ± 2%, P < 0.00001 vs untreated cells) in P-NETs cells and these effects were abolished in FLNA silenced cells. In conclusion, we demonstrated that FLNA plays a crucial role in SST2 expression and signalling, angiogenesis, cell adhesion and cell migration in P-NETs and in QGP1 cell line, suggesting a possible role of FLNA in determining the different responsiveness to SS analogues observed in P-NET patients.

Temozolomide-based combination for advanced neuroendocrine neoplasms: a systematic review of the literature

BACKGROUND

In this systematic review, we explored the value of using temozolomide (TMZ)-based combinations for advanced neuroendocrine neoplasms (NENs).

METHODS

Database search were conducted using the terms 'NENs' and 'TMZ' and 'systemic therapy.' Outcomes of interest included progression-free survival and overall survival, toxicities and tumor response.

RESULTS

In total, 16 trials including 348 patients were included. Median progression-free survival ranged from 6 to 31 months. The disease control rate ranged from 65 to 100%. Frequently reported grade 3/4 toxicities were leukopenia, lymphopenia and elevated transaminases.

CONCLUSION

The published clinical data suggest that TMZ-based combination with some anticancer agents (especially capecitabine) could be an effective treatment option for advanced low-intermediate grade NENs.

Unusual endoscopic findings of gastric neuroendocrine tumor

Gastric neuroendocrine tumor (NET) is sometimes found as a submucosal tumor on upper gastrointestinal endoscopy. Gastric NET with malignant profile and neuroendocrine carcinoma (NEC) show various forms which are difficult to distinguish from gastric cancer and other disease. We report a case of a cauliflower-shaped NET of the stomach. A 61-year-old man was referred to our hospital with a complaint of abdominal fullness. Upper gastrointestinal endoscopic examination revealed an unusual, whitish cauliflower-shaped tumor that belongs to Borrmann type I on the lesser curvature of the gastric antrum. Histological examination of the biopsy specimen revealed NET G2, because the tumor cells were CD56- and synaptophysin-positive by immunohistochemical analysis. A distal gastrectomy with D2 lymphadenectomy was performed. A recurrence in the liver was revealed by follow up computed tomography after 11 months from operation. Combined chemotherapy with irinotecan (CPT-11) plus cisplatin (CDDP) was treated. The patient achieved a partial response, but he died after 31 months from gastrectomy. There is no independent, large-scaled prospective study and no standard treatment for gastric NETs with distant metastases. Our case is reported with a literature review of the treatment of metastatic gastric NET G2.

Somatostatin analogs for gastric carcinoids: For many, but not all

Gastric carcinoids (GCs) are classified as: type I, related to hypergastrinemia due to chronic atrophic gastritis (CAG), type II, associated with Zollinger-Ellison syndrome in multiple endocrine neoplasia type 1, and type III, which is normogastrinemic. The management of type-I gastric carcinoids (GC1s) is still debated, because of their relatively benign course. According to the European Neuroendocrine Tumor Society guidelines endoscopic resection is indicated whenever possible; however, it is not often feasible because of the presence of a multifocal disease, large lesions, submucosal invasion or, rarely, lymph node involvement. Therefore, somatostatin analogs (SSAs) have been proposed as treatment for GC1s in view of their antisecretive, antiproliferative and antiangiogenic effects. However, in view of the high cost of this therapy, its possible side effects and the relatively benign course of the disease, SSAs should be reserved to specific subsets of “high risk patients”, i.e., those patients with multifocal or recurrent GCs. Indeed, it is reasonable that, after the development of a gastric neuroendocrine neoplasm in patients with a chronic predisposing condition (such as CAG), other enterochromaffin-like cells can undergo neoplastic proliferation, being chronically stimulated by hypergastrinemia. Therefore, definite indications to SSAs treatment should be established in order to avoid the undertreatment or overtreatment of GCs.

Ileal neuroendocrine tumors and heart: not only valvular consequences

Ileal neuroendocrine tumors (NETs) often progress slowly, but because of their generally nonspecific symptoms, they have often metastasized to local lymph nodes and to the liver by the time the patient presents. Biochemically, most of these patients have increased levels of whole blood serotonin, urinary 5-hydroxyindoleacetic acid, and chromogranin A. Imaging work-up generally comprises computed tomography or magnetic resonance imaging and somatostatin receptor scintigraphy, or in recent years positron emission tomography with 68Ga-labeled somatostatin analogs, allowing for detection of even sub-cm lesions. Carcinoid heart disease with affected leaflets, mainly to the right side of the heart, is a well-known complication and patients routinely undergo echocardiography to diagnose and monitor this. Multitasking surgery is currently recognized as first-line treatment for ileal NETs with metastases and carcinoid heart disease. Open heart surgery and valve replacement are advocated in patients with valvular disease and progressive heart failure. When valvulopathy in the tricuspid valve results in right-sided heart failure, a sequential approach, performing valve replacement first before intra-abdominal tumor-reductive procedures are conducted, reduces the risk of bleeding. Metastases to the myocardium from ileal NETs are seen in <1-4.3% of patients, depending partly on the imaging technique used, and are generally discovered in those affected with widespread disease. Systemic treatment with somatostatin analogs, and sometimes alpha interferon, is first-line medical therapy in metastatic disease to relieve hormonal symptoms and stabilize the tumor. This treatment is also indicated when heart metastases are detected, with the addition of diuretics and fluid restriction in cases of heart failure. Myocardial metastases are rarely treated by surgical resection.

Efficacy of somatostatin analogues in the treatment of neuroendocrine tumours based on the results of recent clinical trials

Due to their inhibitory effects on hormone secretion, somatostatin analogues are of pivotal importance in the symptomatic treatment of hormone-secreting neuroendocrine tumours. Although several earlier clinical observations supported the view that these biological agents are capable of inhibiting the growth of neuroendocrine tumours, the PROMID study published in 2009 was the first to confirm the inhibitory effect of octreotide on tumour growth and demonstrated the prolongation of progression free survival. These findings have been confirmed and extended by the most recent CLARINET trial with lanreotide published in 2014. Somatostatin analogues are capable of inhibiting tumour growth and stabilizing disease irrespective of the hormonal activity of the tumour and, therefore, their applicability is expected to be extended to the treatment of hormonally inactive neuroendocrine tumours, as well. Orv. Hetil., 2014, 155(48), 1908–1912.

Nordic guidelines 2014 for diagnosis and treatment of gastroenteropancreatic neuroendocrine neoplasms

BACKGROUND

The diagnostic work-up and treatment of patients with neuroendocrine neoplasms (NENs) has undergone major recent advances and new methods are currently introduced into the clinic. An update of the WHO classification has resulted in a new nomenclature dividing NENs into neuroendocrine tumours (NETs) including G1 (Ki67 index ≤ 2%) and G2 (Ki67 index 3-20%) tumours and neuroendocrine carcinomas (NECs) with Ki67 index > 20%, G3. Aim. These Nordic guidelines summarise the Nordic Neuroendocrine Tumour Group's current view on how to diagnose and treat NEN-patients and are meant to be useful in the daily practice for clinicians handling these patients.

Zollinger-Ellison syndrome: recent advances and controversies

PURPOSE OF REVIEW

To review the recent advances and current controversies in patients with Zollinger-Ellison syndrome (ZES).

RECENT FINDINGS

Recent advances in the management of ZES include: improved understanding of the pathogenesis of gastrinoma and pancreatic neuroendocrine tumors, new prognostic classification systems, new diagnostic algorithms, more sensitive localization studies, new treatment strategies including improved control of gastric acid secretion and role for surgery, and new approaches to patients with advanced disease. Controversies include: the best approach to a patient with hypergastrinemia suspected of possibly having ZES, the appropriate gastrin assay to use, the role of surgery in patients with ZES, especially those with multiple endocrine neoplasia type 1, and the precise order of therapeutic modalities in the treatment of patients with advanced disease.

SUMMARY

This review updates clinicians regarding important advances and controversies required to optimally diagnose and manage patients with ZES.

Carcinoid valve disease

OPINION STATEMENT

Carcinoid is a rare neuroendocrine tumor that typically originates in the gastrointestinal tract and can result in a constellation of symptoms, mediated by vasoactive substances, referred to as carcinoid syndrome. Carcinoid valve and heart disease is characterized by the plaque-like, endocardial fibrous tissue deposits, primarily affecting the right heart endocardium and valves, which result as a consequence of the disease process. Potential mechanisms for the carcinoid valve disease include the complex role of excess serotonin and its interaction with serotonin receptors and transporters. Carcinoid valve and heart disease is a frequent occurrence in patients with carcinoid syndrome and is accountable for substantial morbidity and mortality. Cardiac surgery remains the most effective treatment option for carcinoid valve disease and a multidisciplinary approach at an experienced center is recommended for patients with metastatic carcinoid and carcinoid heart disease.

[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.