GEP-NETs update: Biotherapy for neuroendocrine tumours

From biology to clinical practice: antiproliferative effects of somatostatin analogs in neuroendocrine neoplasms

Somatostatin analogs (SSA), specifically octreotide and lanreotide, have demonstrated antiproliferative effects in patients with neuroendocrine tumors (NET), a group of rare malignancies of diverse origin and presentation. A prominent feature of NET cells is the expression of G protein-coupled receptors called somatostatin receptors (SSTR). Although these SSTR are not uniformly present in NET, they can be instrumental in the diagnosis and treatment of NET. Apart from their application in nuclear imaging and radionuclide therapy, SSA have proven invaluable in the treatment of hormonal syndromes associated with certain NET (antisecretory effects of SSA), but it took more than two decades to convincingly demonstrate the antiproliferative effects of SSA in metastatic NET with the two pivotal studies PROMID and CLARINET. The current review summarizes three decades of SSA treatment and provides an overview of the clinical trial landscape for SSA monotherapy and combination therapy, including clinical implications and quality of life aspects, as well as ongoing fields of research.

High-Dose Somatostatin Analogs for the Treatment of Neuroendocrine Neoplasms: where are we Now?

OPINION STATEMENT

Neuroendocrine tumors (NET) represent a complex and heterogeneous group of malignancies arising from the diffuse endocrine cells and other cells derived from the neural crest. Advanced disease is observed at diagnosis in more than one-third of patients. Somatostatin analogs (SSA) are the cornerstone in advanced well-differentiated NET treatment. Unfortunately, most patients will eventually develop resistance to SSA treatment by different mechanisms that are not fully understood. In some cases of refractory carcinoid syndrome or progressive disease, the increase of SSA dose may help to reach out a symptomatic and/or tumor growth control. The clinical evidence behind above-label SSA administration is limited and should be individualized and discussed patient by patient. Some questions regarding high-dose SSA use are unsolved, such as the optimal dose to use, the frequency of administration, or the need of deepen molecular understanding that could help to adequately select patients for this approach.

Recent Advances in the Diagnosis and Management of Carcinoid Syndrome

Carcinoid syndrome, a paraneoplastic condition linked with the release of multiple humoral factors, affects around 30-40% of patients with well-differentiated neuroendocrine tumours. Carcinoid syndrome has a major and unfavourable impact on patients' quality of life; it raises costs when compared to non-functioning neuroendocrine tumours; and it causes patients' lifestyles to alter, such as food, job, physical activity, and social life. Somatostatin analogues have been the first-line therapy for individuals with neuroendocrine tumours and carcinoid disease for decades. While these drugs give considerable relief from carcinoid syndrome symptoms, clinical progression is unavoidable, necessitating further research into newer treatment measures. Carcinoid tumours are sometimes difficult to diagnose because of their vague or nonspecific symptoms. There have been several advancements in all aspects of carcinoid syndrome, as well as novel therapeutics, in the previous few years. New epidemiological studies show that it is becoming more common; increasing insights into the pathogenesis of its various clinical manifestations and its natural history: definition of prognostic factors; new methods to verify its presence; the development of new drugs to treat its various manifestations, both initially and in somatostatin-refractory cases; and an increased understanding of the pathogenesis, natural history, and management of the disease. An all language literature search was conducted on MEDLINE, COCHRANE, EMBASE, and Google Scholar till November 2021. The following search strings and Medical Subject Headings (MeSH) terms were used: "Recent advances", "Carcinoid syndrome", "Neuroendocrine Neoplasms" and "Carcinoid heart disease". We comprehensively reviewed the literature on the pathogenesis, clinical features, and newer treatment modalities for Carcinoid Syndrome. Recent advancements in research and management have resulted from advances in our understanding of the aetiology of carcinoid syndrome. The development of molecular indicators of aggressiveness improved serum tumour markers, and the molecular aetiology of carcinoid heart disease are all possible because of advances in molecular biology. We conducted a comprehensive review to update knowledge regarding the pathophysiology, diagnostic protocols, and current and newer treatments for carcinoid syndrome, which presently requires a multidisciplinary approach, due to the complexity of the illness's aetiology, diagnosis, and therapy.

Time to Sustained Improvement in Bowel Movement Frequency with Telotristat Ethyl: Analyses of Phase III Studies in Carcinoid Syndrome

Background

Telotristat ethyl is approved to treat carcinoid syndrome diarrhea in combination with somatostatin analogs. In TELESTAR and TELECAST phase III studies, patients with carcinoid syndrome received telotristat ethyl 250 or 500 mg 3 times per day (tid) or placebo tid in addition to somatostatin analogs. The aim of this prespecified analysis was to examine the time to reductions in bowel movements (BMs) in the TELESTAR and TELECAST studies using survival analysis methods.

Methods

First occurrence of sustained response was defined as the time to the first day of 2 consecutive weeks with a mean BM frequency improvement of ≥ 30% from baseline during the 12-week double-blind treatment periods. Time to first ≥ 30% worsening in BM frequency was also measured. Treatments were compared with the log-rank test; Cox regression models provided point and confidence interval estimates of the hazard ratios for each trial.

Results

In TELESTAR and TELECAST, majority of patients (69%) on telotristat ethyl experienced a sustained ≥ 30% improvement in BM frequency. The median time to sustained reduction of at least 30% in BM frequency was significantly faster (fewer days to onset) for telotristat ethyl compared with placebo in both TELESTAR (250 mg, HR = 2.3 [95% CI, 1.3–4.1, P = 0.004]; 500 mg, HR = 2.2 [95% CI, 1.2–3.9, P = 0.009]) and TELECAST (250 mg, HR = 3.9 [95% CI, 1.6–11.1, P = 0.003]; 500 mg, HR = 4.2 [95% CI, 1.7–11.7, P = 0.002]). In TELECAST, 42% of patients on placebo experienced sustained worsening in BM frequency compared with 20% on telotristat ethyl; no significant difference was observed in TELESTAR.

Conclusion

The time of onset of sustained BM frequency improvement mean and range are important when considering use of telotristat ethyl in patients with carcinoid syndrome diarrhea. Telotristat ethyl may also reduce sustained worsening in BM frequency.

Trial Registration

ClinicalTrials.gov Identifiers: NCT01677910, NCT02063659

Multiple endocrine neoplasia type 1 (MEN-1) and neuroendocrine neoplasms (NENs)

Neuroendocrine neoplasms (NENs) are relatively rare neoplasms with 6.4-times increasing age-adjusted annual incidence during the last four decades. NENs arise from neuroendocrine cells, which release hormones in response to neuronal stimuli and they are distributed into organs and tissues. The presentation and biological behaviour of the NENs are highly heterogeneous, depending on the organ. The increased incidence is mainly due to increased awareness and improved detection methods both in the majority of sporadic NENs (non-inherited), but also the inherited groups of neoplasms appearing in at least ten genetic syndromes. The most important one is multiple endocrine neoplasia type 1 (MEN-1), caused by mutations in the tumour suppressor gene MEN1. MEN-1 has been associated with different tumour manifestations of NENs e.g. pancreas, gastrointestinal tract, lungs, thymus and pituitary. Pancreatic NENs tend to be less aggressive when arising in the setting of MEN-1 compared to sporadic pancreatic NENs. There have been very important improvements over the past years in both genotyping, genetic counselling and family screening, introduction and validation of various relevant biomarkers, as well as newer imaging modalities. Alongside this development, both medical, surgical and radionuclide treatments have also advanced and improved morbidity, quality of life and mortality in many of these patients. Despite this progress, there is still space for improving insight into the genetic and epigenetic factors in relation to the biological mechanisms determining NENs as part of MEN-1. This review gives a comprehensive update of current evidence for co-occurrence, diagnosis and treatment of MEN-1 and neuroendocrine neoplasms and highlight the important progress now finding its way to international guidelines in order to improve the global management of these patients.

Targeted Cancer Therapy: What's New in the Field of Neuroendocrine Neoplasms?

Neuroendocrine tumors (NETs) are a heterogeneous family of neoplasms of increasing incidence and high prevalence due to their relatively indolent nature. Their wide anatomic distribution and their characteristic ability to secrete hormonally active substances pose unique challenges for clinical management. They are also characterized by the common expression of somatostatin receptors, a target that has been extremely useful for diagnosis and treatment (i.e., somatostatin analogues (SSAs) and peptide-receptor radionuclide therapy (PRRT)). Chemotherapy is of limited use for NETs of non-pancreatic origin, and the only approved targeted agents for advanced progressive NETs are sunitinib for those of pancreatic origin, and everolimus for lung, gastrointestinal and pancreatic primaries. Despite recent therapeutic achievements, thus, systemic treatment options remain limited. In this review we will discuss the state-of-the-art targeted therapies in the field of NETs, and also future perspectives of novel therapeutic drugs or strategies in clinical development, including recently presented results from randomized trials of yet unapproved antiangiogenic agents (i.e., pazopanib, surufatinib and axitinib), PRRT including both approved radiopharmaceuticals (177Lu-Oxodotreotide) and others in development (177Lu-Edotreotide, 177Lu-Satoreotide Tetraxetan), immunotherapy and other innovative targeted strategies (antibody-drug conjugates, bites,…) that shall soon improve the landscape of personalized treatment options in NET patients.

Gastroenteropancreatic neuroendocrine neoplasms and inflammation: A complex cross-talk with relevant clinical implications

Neuroendocrine neoplasms (NENs) are a group of tumors originating from the neuroendocrine system. They mainly occur in the digestive system and the respiratory tract. It is well-know a strict interaction between neuroendocrine system and inflammation, which can play an important role in NEN carcinogenesis. Inflammatory mediators, which are produced by the tumor microenvironment, can favor cancer induction and progression, and can promote immune editing. On the other hand, a balanced immune system represents a relevant step in cancer prevention through the elimination of dysplastic and cancer cells. Therefore, an inflammatory response may be both pro- and anti-tumorigenic. In this review, we provide an overview concerning the complex interplay between inflammation and gastroenteropancreatic NENs, focusing on the tumorigenesis and clinical implications in these tumors.

New and emerging systemic therapy options for well-differentiated gastroenteropancreatic neuroendocrine tumors

Introduction: Well-differentiated gastroenteropancreatic (GEP) neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms with a wide range of clinical behavior. Multiple treatment modalities exist, including novel and emerging systemic options, and an understanding of the advantages and disadvantages of each is imperative for optimizing the outcomes of patients with GEP-NETs.Areas covered: While surgical resection remains the preferred treatment for localized well-differentiated GEP-NETs, treatment of unresectable disease depends on its extent, location, and distribution as well as underlying aspects of tumor biology. Isolated hepatic metastases can be successfully treated with liver-directed therapies such as hepatic arterial based therapies or ablation. Diffuse metastatic disease often requires systemic treatments such as molecular-targeted therapeutics, peptide receptor radionuclide therapy (PRRT), or traditional chemotherapy. Somatostatin analogs are often the primary treatment option capable of simultaneously inhibiting hormone production and slowing tumor growth.Expert opinion: Recent advances in systemic treatment options for advanced well-differentiated GEP-NETs have emerged due to an improved understanding of the molecular mechanisms responsible for tumor development and progression. Future research is needed to determine the optimal indications for and sequencing of these novel therapies.

Carcinoid Syndrome: Updates and Review of Current Therapy

OPINION STATEMENT

Carcinoid syndrome (CS) is a complex disorder caused by functional neuroendocrine tumors (NETs). This debilitating disease is characterized by hyper-secretion of biologically active substances eliciting major hormonal symptoms burden and fibrotic changes that are often challenging for management. There have been a number of insights that have substantially advanced treatments since the introduction of somatostatin analogs (SSAs). Second-line treatments are needed in a substantial proportion of patients with advanced disease that have uncontrolled hormone secretion on the highest labeled doses of SSAs. International guidelines suggest several available options including dose escalation of SSAs, interferon alpha, everolimus, radionuclide therapy, liver-directed therapies, and the novel tryptophan hydroxylase 1 inhibitor, telotristat ethyl. The clear preference of one second-line therapy over the other is not stated since their relative and long-term efficacy are largely unknown, and standardized approach of hormonal response assessment is lacking in the literature. In the clinical setting, the treatment of CS is guided in conjunction with patients' performance status, tumor origin, grade, stage, and growth rate, with regard to both anti-hormonal, as well as anti-proliferative effect. There is an unmet need for further well-designed randomized placebo-controlled and head-to-head studies that systematically assess CS symptom control and biochemical response following a specific intervention.

Effects of novel somatostatin-dopamine chimeric drugs in 2D and 3D cell culture models of neuroendocrine tumors

Control of symptoms related to hormonal hypersecretion by functioning neuroendocrine tumors (NETs) is challenging. New therapeutic options are required. Since novel in vitro tumor models seem to better mimic the tumor in vivo conditions, we aimed to study the effect of somatostatin and dopamine receptor agonists (octreotide and cabergoline, respectively) and novel somatostatin-dopamine chimeric multi-receptor drugs (BIM-065, BIM-23A760) using 2D (monolayer) and 3D (spheroids) cultures. Dose-response studies in 2D and 3D human pancreatic NET cell cultures (BON-1 and QGP-1) were performed under serum-containing and serum-deprived conditions. Cell proliferation, somatostatin and dopamine receptor expression (SSTs and D2R), apoptosis, lactate dehydrogenase, as well as serotonin and chromogranin A (CgA) release were assessed. The following results were obtained. 3D cultures of BON-1/QGP-1 allowed better cell survival than 2D cultures in serum-deprived conditions. SSTs and D2R mRNA levels were higher in the 3D model vs 2D model. Octreotide/cabergoline/BIM-065/BIM-23A760 treatment did not affect cell growth or spheroid size. In BON-1 2D-cultures, only BIM-23A760 significantly inhibited CgA release -this effect being more pronounced in 3D cultures. In BON-1 2D cultures, cabergoline/BIM-065/BIM-23A760 treatment decreased serotonin release (maximal effect up to 40%), being this effect again more potent in 3D cultures (up to 67% inhibition; with BIM-23A760 having the most potent effects). In QGP-1, cabergoline/BIM-065 treatment decreased serotonin release only in the 3D model. In conclusion, cultures of NET 3D spheroids represent a promising method for evaluating cell proliferation and secretion in NET cell-line models. Compared to 2D models, 3D models grow relatively serum independent. In 3D model, SST-D2R multi-receptor targeting drugs inhibit CgA and serotonin secretion, but not NET cell growth.

The emerging role of targeted therapies for advanced well-differentiated gastroenteropancreatic neuroendocrine tumors

INTRODUCTION

Gastroenteropancreatic (GEP) neuroendocrine tumors (NETs) are unique and complex neoplasms, exhibiting a wide spectrum of diverse clinical behaviors. The contemporary management of well-differentiated GEP-NETs is marked by the availability of a wide range of targeted therapies. Areas Covered: For patients with localized or oligometastatic disease, surgical resection remains the preferred approach and is associated with excellent long-term outcomes. For patients with unresectable but isolated liver metastases, multiple liver-directed therapies, including hepatic arterial based therapies and ablative techniques, exist. For patients with metastatic and progressive disease, a number of systemic therapies exist: molecular targeted agents, peptide receptor radionuclide therapy (PRRT), and systemic chemotherapy. Furthermore, somatostatin analogs (SSA) are an important component of therapy, both effectively controlling symptoms of hormonal overproduction and contributing to slowing tumor progression. Expert Opinion: In the near future, advances in our understanding of tumor biology, genetics, immunology, nanotechnology, and radiation pharmacology should only continue to expand the availability of targeted therapies, improving the outcomes of patients with GEP-NETs. We herein review the management of advanced well-differentiated GEP-NETS with a particular emphasis on the role of targeted therapies.

Peptide Receptor Radionuclide Therapy as a Novel Treatment for Metastatic and Invasive Phaeochromocytoma and Paraganglioma

At present there is no clinical guideline or standardised protocol for the treatment of metastatic or invasive phaeochromocytoma and paraganglioma (collectively known as PPGL) due to the rarity of the disease and the lack of prospective studies or extended national databases. Prognosis is mainly determined by genetic predisposition, tumour burden, rate of disease progression, and location of metastases. For patients with progressive or symptomatic disease that is not amenable to surgery, there are various palliative treatment options available. These include localised therapies including radiotherapy, radiofrequency, or cryoablation, as well as liver-directed therapies for those patients with hepatic metastases (e.g., transarterial chemoembolisation) and systemic therapies including chemotherapy or molecular targeted therapies. There is currently intense research interest in the value of radionuclide therapy for neuroendocrine tumours, including phaeochromocytoma and paraganglioma, with either iodine-131 (131I)-radiolabelled metaiodobenzylguanidine or very recently peptide receptor radionuclide therapy (PRRT), and the most important contemporary clinical studies will be highlighted in this review. The studies to date suggest that PRRT may induce major clinical, biochemical, and radiological changes, with 177Lu-DOTATATE being most efficacious and presenting less toxicity than 90Y-DOTATATE. Newer combination therapies with combined radioisotopes, or combinations with chemotherapeutic agents, also look promising. Given the favourable efficacy, logistic, and safety profiles, we believe that PRRT will probably become the standard treatment for inoperable metastatic PPGL in the near future, but we await data from definitive randomised controlled trials to understand its role.

Role of the tumor microenvironment in digestive neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) represent a group of heterogeneous tumors whose incidence increased over the past few years. Around half of patients already present with metastatic disease at the initial diagnosis. Despite extensive efforts, cytotoxic and targeted therapies have provided only limited efficacy for patients with metastatic GEP-NETs, mainly due to the development of a certain state of resistance. One factor contributing to both the failure of systemic therapies and the emergence of an aggressive tumor phenotype may be the tumor microenvironment (TME), comprising dynamic and adaptative assortment of extracellular matrix components and non-neoplastic cells, which surround the tumor niche. Accumulating evidence shows that the TME can simultaneously support both tumor growth and metastasis and contribute to a certain state of resistance to treatment. In this review, we summarize the current knowledge of the TME of GEP-NETs and discuss the current therapeutic agents that target GEP-NETs and those that could be of interest in the (near) future.

The Treatment Landscape and New Opportunities of Molecular Targeted Therapies in Gastroenteropancreatic Neuroendocrine Tumors

Neuroendocrine neoplasms (NENs) are a heterogeneous group of neoplasms that originate from neuroendocrine stem cells and express both neural and endocrine markers. They are found in almost every organ, and while NENs are mostly associated with slow growth, complications due to the uncontrolled secretion of active peptides, and metastatic disease, may significantly impair the quality of life and can ultimately lead to the death of affected individuals. Expanding knowledge of the genetic, epigenetic, and proteomic landscapes of NENs has led to a better understanding of their molecular pathology and consequently increased treatment options for patients. Here, we review the principal breakthroughs in NEN treatment management, owing largely to omics technologies over the last few years, current recommendations of systemic treatment, and ongoing research into the identification of predictive and response biomarkers based on molecular targeted therapies.

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.

Supportive therapy in gastroenteropancreatic neuroendocrine tumors: Often forgotten but important

Neuroendocrine tumors (NETs) are a group of rare and heterogeneous malignancies that can develop in various organs. A significant number of gastroenteropancreatic neuroendocrine tumours (GEP-NETs) is functionally active and presents with symptoms related to the secretion of biologically active substances, leading to the development of distinct clinical syndromes. There are various therapeutic approaches for GEP-NETs, including curative surgery, palliative surgery, local-ablative and loco-regional therapies as well as systemic therapeutic options including peptide receptor radionuclide therapy, cytotoxic therapy, and molecularly targeted therapies. Specific supportive therapy of patients with NETs includes management or prevention of hormone-related clinical syndromes and paraneoplastic states. Supportive therapy plays a key role in NET treatment. Supportive therapy includes debulking surgery and interventional radiologic techniques to reduce tumour bulk or load, as well as systemic medical treatment options to manage or prevent hypersecretion syndromes and treatment-related side effects. Supportive therapies are a type of of comprehensive treatment addressing the patient as a whole person throughout the process of NET treatment. Therefore, supportive therapy also encompasses psychosocial support, expert nursing, nutritional support and management of cancer related pain.

Advanced neuroendocrine tumours of the small intestine and pancreas: clinical developments, controversies, and future strategies

In this Review, we discuss clinical developments and controversies in the treatment of neuroendocrine tumours (NETs) that are relevant for clinicians and clinical researchers. We describe advances in genetics, blood-based biomarkers, functional imaging, and systemic therapy of advanced NETs and discuss results of recent phase 3 studies, systemic treatment of advanced disease with peptide receptor radionuclide therapy, biotherapy, chemotherapy, and molecularly targeted therapy, and the potential role of immunotherapy in the treatment of NETs. Suggested treatment algorithms for NETs of ileal or jejunal origin and of pancreatic origin are presented.

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.

Long-acting somatostatin analogues in the treatment of unresectable/metastatic neuroendocrine tumors

Neuroendocrine tumors (NETs) are a relatively rare and heterogeneous group of neoplasms with an annual incidence of ~35 cases per 100,000 people in the United States. The updated World Health Organization (WHO) classification system of gastroenteropancreatic (GEP)-NETs categorizes these tumors according to site of origin, clinical syndrome, and degree of differentiation. Well-differentiated NETs arising from the gastrointestinal tract or lungs (formerly known as carcinoid tumors) are often indolent and slow-growing. In contrast, poorly differentiated neuroendocrine carcinomas (NECs) are aggressive and have a poor prognosis. Due to their insidious onset, most NETs are diagnosed at an advanced stage and a curative approach is not possible. In these patients, medical therapy is limited to disease control, including relief of symptoms that arise from overproduction of peptide hormones by the tumors. Somatostatin analogues (SSAs) have remained the mainstay of symptoms control. In addition to symptoms control, clinical data also support an anti-proliferative effect of SSAs in patients with well- to moderately differentiated NETs. Long-acting SSAs have greatly facilitated their use. This review will focus on two long-acting SSAs, octreotide LAR and lanreotide, and their use in the clinical setting. Information necessary to assess their relative merits is summarized. We conclude these two therapies are interchangeable making value a very important consideration in their use.

Proof of Therapeutic Efficacy of a 177Lu-Labeled Neurotensin Receptor 1 Antagonist in a Colon Carcinoma Xenograft Model

Increased expression of neurotensin receptor 1 (NTR1) has been shown in a large number of tumor entities such as pancreatic or colon carcinoma. Hence, this receptor is a promising target for diagnostic imaging and radioligand therapy. Using the favorable biodistribution data of the NTR1-targeting agent ¹¹¹In-3BP-227, we investigated the therapeutic effect of its ¹⁷⁷Lu-labeled analog on the tumor growth of NTR1-positive HT29 colon carcinoma xenografts. Methods: 3BP-227 was labeled with ¹⁷⁷Lu. To assess its biodistribution properties, SPECT and CT scans of HT29-xenografted nude mice injected with ¹⁷⁷Lu-3BP-227 were acquired, and ex vivo tissue activity was determined. To evaluate therapeutic efficacy, 2 groups of mice received the radiopharmaceutical in a median dose of either 165 MBq (129-232 MBq, n = 10) or 110 MBq (82-116 MBq, n = 10), whereas control mice were injected with vehicle (n = 10). Tumor sizes and body weights were monitored for up to 49 d. Renal function and histologic morphology were evaluated. Results: Whole-body SPECT/CT images allowed clear tumor visualization with low background activity and high tumor-to-kidney and -liver ratios. Ex vivo biodistribution data confirmed high and persistent uptake of ¹⁷⁷Lu-3BP-227 in HT29 tumors (19.0 ± 3.6 vs. 2.7 ± 1.6 percentage injected dose per gram at 3 and 69 h after injection, respectively). The application of ¹⁷⁷Lu-3BP-227 resulted in a distinct delay of tumor growth. Median tumor doubling time for controls was 5.5 d (interquartile range [IQR], 2.8-7.0), compared with 17.5 d (IQR, 5.5-22.5 d) for the 110-MBq and 41.0 d (IQR, 27.5-55.0) for the 165-MBg group. Compared with controls, median relative tumor volume at day 23 after injection was reduced by 55% (P = 0.034) in the 110-MBq and by 88% (P < 0.01) in the 165-MBq group. Renal histology and clinical chemistry results did not differ between radiotherapy groups and controls, suggesting absence of therapy-induced acute renal damage. Conclusion: These data demonstrate that the novel NTR1-targeting theranostic agent 3BP-227 is an effective and promising candidate for radioligand therapy, with a favorable preliminary safety profile and high potential for clinical translation.

Small cell neuroendocrine carcinoma of the paranasal sinus with intraoral involvement: Report of a rare case and review of the literature

The diffuse neuroendocrine system continues to be an enigmatic topic of study in pathology due to its controversial embryologic origins, biology and a variety of tumors engendered. Originally thought to be localized to the classic neuroendocrine organs (pituitary, thyroid, pancreas and adrenal medulla), the neuroendocrine cells are now known to be distributed in every organ system of the body. A number of human diseases have been linked to aberrations in the functioning of the neuroendocrine cells. Neoplasms of the neuroendocrine system can thus occur in myriad primary sites and range in behavior from benign to lethal. Small cell neuroendocrine carcinoma (SNEC) is a high-grade neuroendocrine tumor, rarely presenting in the sinonasal region. This article reports a case of a 68-year-old male patient with primary paranasal SNEC showing intraoral involvement. The diagnosis is based on a thorough clinical, histopathological and immunohistochemical workup to differentiate it from the other small round blue cell tumors.

Management of controversial gastroenteropancreatic neuroendocrine tumour clinical situations with somatostatin analogues: results of a Delphi questionnaire panel from the NETPraxis program

BACKGROUND

There are clinical situations (CS) in which the use of somatostatin analogs (SSAs) in patients with neuroendocrine tumors (NET) is controversial due to lack of evidence. A Delphi study was conducted to develop common treatment guidelines for these CS, based on clinical practice and expert opinion of Spanish oncologists.

METHODS

A scientific committee identified 5 CS with a common core (c-c) [non-functioning NET, not susceptible of surgery/locoregional therapy, Ki67 < 10 % (except for CS5: >10 %), ECOG ≤ 2], and controversy regarding use of SSAs, and prepared a Delphi questionnaire of 48 treatment statements. Statements were rated on a 1 (completely disagree) to 9 (completely agree) scale. Responses were grouped by tertiles: 1-3: Disagreement, 4-6: Neutral, 7-9: Agreement. Consensus was reached when the responses of ≥2/3 participants were located in the same tertile as the median value of all reported responses for that statement.

RESULTS

Sixty five (81.2 %) of 80 invited oncologists with experience in the management of NETs answered a first round of the questionnaire and 57 (87.7 %) of those 65 answered a second round (mean age 43.5 years; 53.8 % women; median time of experience 9 years). Consensus was obtained in 42 (36 agreement and 6 disagreement) of the 48 statements (87.5 %). Regarding CS1 (Enteropancreatic NET, c-c, non-progressive in the last 3-6 months), overall, SSA treatment is recommended (a wait and see approach is anecdotal and reserved for fragile patients or with low tumor load or ki-67 < 2 %); CS2 (Pancreatic NET, c-c), overall, SSA monotherapy is recommended, except when high tumor load or tumor progression exists, where combination therapy would be considered; CS3 [Gastroenteropancreatic (GEP)-NET, c-c, in treatment with anti-proliferative dose of SSA and progressing], overall, SSA maintenance is recommended at the time of progression, with or without adding molecular targeted drugs; CS4 (GEP-NET, c-c, and negative octreoscan®), SSA in monotherapy is only considered in low-risk patients (low tumor load and Ki-67 < 5 %); CS5 [GEP-NET, c-c (ki67 > 10 %), and positive octreoscan®], monotherapy with SSA is mainly considered in patients with comorbidities.

CONCLUSION

Several recommendations regarding use of SSAs in controversial NET CS were reached in consensus and might be considered as treatment guideline.

Liposomal doxorubicin for active targeting: surface modification of the nanocarrier evaluated in vitro and in vivo: challenges and prospects

Due to the inability of classical chemotherapeutic agents to exclusively target tumor cells, these treatments are associated with severe toxicity profiles. Thus, long-circulating liposomes have been developed in the past to enhance accumulation in tumor tissue by passive targeting. Accordingly, commercially available liposomal formulations of sterically stabilized liposomal doxorubicin (Caelyx^®, Doxil^®, Lipodox^®) are associated with improved off-target profiles. However, these preparations are still not capable to selectively bind to target cells. Thus, in an attempt to further optimize existing treatment schemes immunoliposomes have been established to enable active targeting of tumor tissues. Recently, we have provided evidence for therapeutic efficacy of anti-IGF1R-targeted, surface modified doxorubicin loaded liposomes. Our approach involved a technique, which allows specific post-modifications of the liposomal surface by primed antibody-anchor conjugates thereby facilitating personalized approaches of commercially available liposomal drugs. In the current study, post-modification of sterically stabilized liposomal Dox was thoroughly investigated including the influence of different modification techniques (PIT, SPIT, SPIT60), lipid composition (SPC/Chol, HSPC/Chol), and buffers (HBS, SH). As earlier in vivo experiments did not take into account the presence of non-integrated ab-anchor conjugates this was included in the present study. Our experiments provide evidence that post-modification of commercially available liposomal preparations for active targeting is possible. Moreover, lyophilisation represents an applicable method to obtain a storable precursor of surface modifying antibody-anchor conjugates. Thus, these findings open up new approaches in patient individualized targeting of chemotherapeutic therapies.

Perspectives for immunotherapy in endocrine cancer

The fight against cancer has seen major breakthroughs in recent years. More than a decade ago, tyrosine kinase inhibitors targeting constitutively activated signaling cascades within the tumor inaugurated a new era of oncological therapy. Recently, immunotherapy with immune checkpoint inhibitors has started to revolutionize the treatment of several malignancies, most notably malignant melanoma, leading to the renaissance and the long-awaited breakthrough of immunooncology. This review provides an overview of the basis of immunotherapy from its initial concepts of anti-tumor immunity and cell-based therapy to the development of immune checkpoint inhibitors and discusses published studies and the perspectives of immunooncology for the treatment of endocrine malignancies.

Systemic Therapies for Advanced Gastrointestinal Carcinoid Tumors

Well-differentiated gastrointestinal neuroendocrine tumors (GINETs) tend to be slow growing, but treatment of advanced disease remains a challenge. Somatostatin analogues (SSAs) are considered standard therapy for carcinoid syndrome. SSAs delay tumor progression in advanced well-differentiated gastroenteropancreatic NETs. Cytotoxic chemotherapy and interferon play a limited role in the treatment of nonpancreatic GINETs. There is no standard approach to treatment of patients with disease progression. Identification of systemic agents with antitumor activity in advanced disease remains an unmet medical need. Enrollment to clinical trials is encouraged; potential therapeutic targets include the vascular endothelial growth factor and mammalian target of rapamycin signaling pathways.

Primary Neuroendocrine Tumor of the Parotid Gland: A Case Report and a Comprehensive Review of a Rare Entity

Neuroendocrine tumors (NETs) comprise a heterogeneous group of malignancies from cells derived from the neural crest with neuroendocrine differentiation. Despite the differences in the site of origin, nomenclature, biological behavior, and functional status, NETs share certain ultrastructural and immunohistochemical features. NETs are relative rare tumors with an annual incidence of 5.76 new cases per 100.000 inhabitants and they usually appear in the gastrointestinal tract or in the pulmonary system. Head and neck NETs are uncommon with limited information regarding frequency, most of them showing small cell carcinoma features. NETs that arise from the salivary glands are exceedingly rare. Regardless of their low frequency, it is imperative to accurately differentiate these tumors from the much more common squamous cell carcinomas and from metastasis from another primary tumor due to the completely different therapeutic approaches and prognosis. The diagnosis is based on the recognition of the typical neuroendocrine architecture and immunohistochemical staining and on an exhaustive work-up. Hereby, we report a case of a moderately differentiated NET of the parotid gland that was treated with a complete parotidectomy. We summarize the clues that led to the final diagnosis and major strategies that were employed to manage the patient. We also perform a comprehensive review of the scarce available literature on this topic.

Inhibition of Peripheral Synthesis of Serotonin as a New Target in Neuroendocrine Tumors

: The carcinoid syndrome represents a set of signs and symptoms associated with neuroendocrine tumors (NETs) that occur primarily when metastases are developed in the liver, resulting in the worsening of quality of life. Serotonin plays a central role in the physiology of carcinoid syndrome by promoting intestinal motility. Somatostatin analogs (SSAs) have widely demonstrated their efficacy as symptomatic relievers of carcinoid syndrome, but this control is ephemeral, being reduced by approximately 50% within the first year. The exact mechanisms of resistance to SSAs are not fully understood, but it is believed that serotonin might be involved. Patients with carcinoid syndrome present with a significant increase in serotonin plasma levels and, consequently, in the soluble urinary metabolite 5-hydroxyindole acetic acid. Telotristat etiprate is a potent inhibitor of tryptophan hydroxylase, a rate-limiting enzyme in the synthesis of serotonin, that has demonstrated in the phase III TELESTAR clinical trial a significant improvement in the control of bowel movements in patients with NETs who have carcinoid syndrome and who have progressed to an SSA. Based on these results, telotristat etiprate has emerged as a potential new option in the treatment algorithm of symptomatic control of functioning NETs. However, some issues need to be clarified, such as the safety profile of the drug outside clinical trials, the benefit in quality of life, and the possible impact on tumor growth, as well as its role within sequencing or combination treatment strategies with pre-existing drugs effective in NET treatment.

IMPLICATIONS FOR PRACTICE

This article reviews the literature about carcinoid syndrome, which affects patients diagnosed with neuroendocrine tumors. Few articles have been published about this syndrome and its pathophysiology. Somatostatin analogs provide symptomatic relief; however, patients may become refractory to this strategy, usually within the first year of treatment. In this context, as an agent with an innovative mechanism of action, telotristat etiprate has demonstrated activity in a phase III trial, and findings may offer a path to an improve quality of life and prolonged survival for certain patients.

Medical treatment for gastro-entero-pancreatic neuroendocrine tumours

Gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs) represents a various family of rare tumours. Surgery is the first choice in GEP-NENs patients with localized disease whilst in the metastatic setting many other treatment options are available. Somatostatin analogues are indicated for symptoms control in functioning tumours. Furthermore they may be effective to inhibit tumour progression. GEP-NENs pathogenesis has been extensively studied in the last years therefore several driver mutations pathway genes have been identified as crucial factors in their tumourigenesis. GEP-NENs can over-express vascular endothelial growth factor (VEGF), basic-fibroblastic growth factor, transforming growth factor (TGF-α and -β), platelet derived growth factor (PDGF), insulin-like growth factor-1 (IGF-1) and their receptors PDGF receptor, IGF-1 receptor, epidermal growth factor receptor, VEGF receptor, and c-kit (stem cell factor receptor) that can be considered as potential targets. The availability of new targeted agents, such as everolimus and sunitinib that are effective in advanced and metastatic pancreatic neuroendocrine tumours, has provided new treatment opportunities. Many trials combing new drugs are ongoing.