Durvalumab plus tremelimumab for the treatment of advanced neuroendocrine neoplasms of gastroenteropancreatic and lung origin

Phase Ib/II study of Pembrolizumab with Lanreotide depot for advanced, progressive Gastroenteropancreatic neuroendocrine tumors (PLANET)

While performing a study of immune checkpoint blockade with the anti-PD-1 antibody pembrolizumab combined with the somatostatin analogue (SSA) lanreotide in patients with low- and intermediate-grade gastroenteropancreatic neuroendocrine tumors (GEP-NETs), we studied whether there were any immune correlates of response to the anti-PD-1 therapy that could guide future attempts to integrate immunotherapy into the treatment of NETs. Patients with grade 1 and 2 GEP-NETs who had progressed on a prior SSA received lanreotide 90 mg subcutaneously and pembrolizumab 200 mg intravenously every 3 weeks until progression or intolerable toxicity. Objective response rate (ORR) at any time in the study, clinical benefit rate (CBR, defined as stable disease or better), progression-free survival (PFS), and overall survival (OS) were measured. Changes in T cell subsets in peripheral blood before and during therapy were analyzed by multiparameter mass cytometry (CyTOF). Archived tissue samples were analyzed for PD-L1 expression and TIL infiltration. Twenty-two (22) patients (GI/pancreatic 14/8, median Ki67 7% [IQR 4, 10%], median 1.5 prior systemic therapies [range 1-4]) were enrolled. Among the GI-NETs, there was one partial response, the CBR was 50%, the median PFS was 8.5 months, and the median OS was 32.7 months. No responses were seen in pancreatic NETs, which had 0% CBR, a PFS of 2.7 months, and an OS of 23.9 months. Of the 16 analyzable tumors, 6 had detectable PD-L1 expression and 15 had detectable TILs. Neither TILs nor PD-L1 expression correlated with ORR or CBR. However, clinical benefit (SD or better) was associated with peripheral blood on-treatment effector memory T cell activation and progressive disease was associated with baseline peripheral blood regulatory T cell (Treg) activation. We conclude that immune checkpoint blockade had low activity in unselected patients with grade 1 and 2 GEP-NETs. Further study of strategies to reduce Treg activation or enhance effector memory activation during immunotherapy is warranted.

Evolving Immunotherapy Strategies in Gastrointestinal Neuroendocrine Neoplasms

OPINION STATEMENT

Treatment for neuroendocrine neoplasms (NENs) is tailored to the tumor's site of origin, grade, and differentiation. NENs are categorized into two main types: well-differentiated neuroendocrine tumors (NETs), which tend to grow more slowly and are less aggressive, and poorly differentiated neuroendocrine carcinomas (NECs), which are highly aggressive and harder to treat. Treatment options for NETs range from somatostatin analogues and mTOR inhibitors to peptide receptor radionuclide therapy (PRRT) with Lutetium-177 dotatate. In cases where the disease progresses more rapidly, cytotoxic chemotherapy may also be considered. In contrast, chemotherapy plays a central role in treating NECs, often following protocols similar to those used for small cell lung cancer. Exciting progress is being made in the development of new therapies for NENs. Inspired by the success of immunotherapy in other cancers, clinical trials have begun to explore its potential in NENs. Early findings suggest that immune checkpoint inhibitors (ICIs) may offer benefits, especially in patients with higher-grade NETs and NECs. However, because NENs have an immunologically "cold" tumor microenvironment-meaning they are less likely to trigger an immune response-new strategies are needed to boost ICI efficacy. To overcome this challenge, researchers are exploring innovative approaches, such as combining dual ICIs or pairing ICIs with other therapeutic agents to make the tumors more responsive to immune attack. Moreover, there is growing enthusiasm for cutting-edge therapies designed to enhance the immune system's ability to recognize and destroy cancer cells. These include bispecific T cell engagers, chimeric antigen receptor T cells, tumor-infiltrating lymphocytes, oncolytic viruses, and cancer vaccines. While their effectiveness in NENs is still being studied, these approaches hold considerable promise, offering new hope for patients with this challenging and complex cancer type.

Selecting systemic treatment for metastatic neuroendocrine tumors of the lung-current evidence and clinical implications

Neuroendocrine tumors (NET) of the lung are a slowly growing subtype of lung cancer that has a different treatment paradigm than aggressive and more common forms of lung neuroendocrine neoplasms (NEN) like small cell lung cancer (SCLC). Current guidelines for metastatic lung NET advocate a handful of treatment options, including somatostatin analogs (SSA), everolimus, temozolomide- or platin-based chemotherapy, and peptide receptor radionuclide therapy (PRRT). However, there is no clear treatment sequence, and the therapy of choice may depend on several factors such as tumor grade / growth rate, tumor burden / symptoms, disease progression status, and somatostatin receptor (SSTR) expression. In order to tailor treatment to each individual patient, the latest scientific findings and patient-specific clinical features must be considered together. This review critically evaluates the available evidence with regards to relevant patient characteristics, inclusion and exclusion criteria, and outcome metrics of clinical trials given the presumed natural disease course. Specific patient subgroups with an unmet therapeutic need are identified and discussed in the context of ongoing clinical trials.

Treatment and management of duodenal gangliocytic paraganglioma: A case report

Gangliocytic paraganglioma (GP) is a rare neuroendocrine tumor primarily found in the duodenum, most commonly in the second and third sections of the duodenum. Diagnosis of GP is based on its distinctive histopathological characteristics, which include three types of tumor cells in varying proportions: i) Epithelioid, ii) spindle-like and iii) ganglion-shaped cells. The distribution of the three tumor cell components varies from case to case and a patient may be easily misdiagnosed if one of the components is predominant. Endoscopic submucosal dissection (ESD) or surgical resection is the ideal treatment for duodenal GP (DGP); however, biotherapy, nuclide therapy, chemotherapy, targeted therapy and immunotherapy can be selected individually for patients with postoperative recurrence, metastasis or not suitable for surgery. In the present study, a male patient with DGP experienced recurrence after ESD surgery, and so received octreotide (Novartis; 30 mg/28 days) for 12 consecutive cycles. The patient had no further symptoms of gastrointestinal bleeding and no new lesions or metastases were observed after 47 months of follow-up.

High-Grade Gastrointestinal Neuroendocrine Carcinomas: Multidisciplinary Approach Can Improve Survival Outcomes

Purpose There is limited evidence for the presentation patterns and outcomes of patients with high-grade gastrointestinal neuroendocrine carcinomas (HG-NEC).

Methods Patients diagnosed with HG-NEC, defined as having a pathological diagnosis of neuroendocrine cancer with an epicenter of cancer in the gastrointestinal tract and Molecular Immunology Borstel-1 index ≥ 20% between May 2014 and May 2022 were retrospectively analyzed for demographic variables, survivals, and prognostic parameters. The primary endpoint of the study was the estimation of median overall survival (OS) by the Kaplan–Meier method.

Results A total of 336 patients were included in the analysis, of whom 283 patients (84%) were started on cancer-directed treatment while 53 patients (16%) were planned for best supportive care. The most common sites of the primary were gallbladder (45%), colorectal (19%), and pancreas (13%), with 253 patients (75%) having metastatic NEC. All treated patients received systemic therapy (commonly platinum and etoposide), while 64 patients (23%) underwent resection of the primary. With a median follow-up of 65.4 (45.6 -85.3) months, the median OS of the entire cohort was 15.8 months. The prospective multidisciplinary tumor (MDT) board decision of classifying patients into resectable, unresectable, and metastatic HG-NEC was prognostic for OS (26.8 vs. 21.1 vs. 13.5 months; p = 0.001). Patients who were able to undergo multimodality therapy (resection and systemic therapy) had improved OS compared with patients on systemic therapy alone (23.1 vs. 14.9 months; p = 0.003).

Conclusion A majority of patients with HG-NEC present with advanced disease. An MDT is essential to deciding initial therapeutic strategies in these patients, with patients undergoing resection and systemic therapy having improved OS.

Current Status of Immunotherapy in Management of Small Bowel Neuroendocrine Tumors

PURPOSE OF REVIEW

This study aims to present the current landscape of immunotherapy in the management of small bowel neuroendocrine tumors and identify ongoing and future targets for improved response.

RECENT FINDINGS

Somatostatin analogs and mTOR inhibitors remain cornerstones of non-surgical treatment, and applications of PRRT in SBNET are promising. Several efforts to replicate the success of immunotherapies in other solid tumors have been attempted in SBNET, with limited responses observed with current immune targets, such as PD-1/PD-L1 and CTLA-4. Epigenetic analyses have suggested a potential role for methylation and histone acetylation in SBNET tumorigenesis that warrant greater exploration. While the incidence of SBNET continues to increase, the number of effective therapies is few. Further elucidation of targetable components of the SBNET immune microenvironment with greater modulatory effects is necessary to improve outcomes in this growing patient population.

Prolonged Response to Dabrafenib/Trametinib in Grade 3 Metastatic Pancreatic Neuroendocrine Tumor (NET G3) with BRAF V600E Mutation

PURPOSE

Treatment of metastatic pancreatic neuroendocrine tumors (pancNETs), particularly grade 2 (G2) and grade 3 (G3), often presents a dilemma in choosing from multiple similarly efficacious therapies. Data on targeted therapies for these tumor types is limited, and this report presents BRAF-targeted therapy as a therapeutic option for metastatic pancNET G3.

METHODS

This is a case report of a patient with G3 pancNET metastatic to the liver, lung, lymph node, and scalp (soft tissue) treated with dabrafenib/trametinib (D/T) in the presence of a BRAF V600E mutation detected in tumor tissue.

RESULTS

This patient has demonstrated an ongoing partial response to therapy at all involved sites for nearly 15 months with minimal side effects attributable to D/T.

CONCLUSION

Dabrafenib/trametinib therapy for BRAF-mutated metastatic pancNETs provides a novel treatment option and, especially in the G3 setting, should be considered a first-line option. Tumor testing for actionable mutations should be undertaken at the time of diagnosis and/or progression to identify novel therapeutic avenues in these rare tumors.

Nivolumab plus platinum-doublet chemotherapy in treatment-naive patients with advanced grade 3 Neuroendocrine Neoplasms of gastroenteropancreatic or unknown origin: The multicenter phase 2 NICE-NEC trial (GETNE-T1913)

The prognosis of patients with advanced high-grade (G3) digestive neuroendocrine neoplasms (NENs) is rather poor. The addition of immune checkpoint inhibition to platinum-based chemotherapy may improve survival. NICE-NEC (NCT03980925) is a single-arm, phase II trial that recruited chemotherapy-naive, unresectable advanced or metastatic G3 NENs of gastroenteropancreatic (GEP) or unknown origin. Patients received nivolumab 360 mg intravenously (iv) on day 1, carboplatin AUC 5 iv on day 1, and etoposide 100 mg/m2/d iv on days 1-3, every 3 weeks for up to six cycles, followed by nivolumab 480 mg every 4 weeks for up to 24 months, disease progression, death or unacceptable toxicity. The primary endpoint was the 12-month overall survival (OS) rate (H0 50%, H1 72%, β 80%, α 5%). Secondary endpoints were objective response rate (ORR), duration of response (DoR), progression-free survival (PFS), and safety. From 2019 to 2021, 37 patients were enrolled. The most common primary sites were the pancreas (37.8%), stomach (16.2%) and colon (10.8%). Twenty-five patients (67.6%) were poorly differentiated carcinomas (NECs) and/or had a Ki67 index >55%. The ORR was 56.8%. Median PFS was 5.7 months (95%CI: 5.1-9) and median OS 13.9 months (95%CI: 8.3-Not reached), with a 12-month OS rate of 54.1% (95%CI: 40.2-72.8) that did not meet the primary endpoint. However, 37.6% of patients were long-term survivors (>2 years). The safety profile was consistent with previous reports. There was one treatment-related death. Nivolumab plus platinum-based chemotherapy was associated with prolonged survival in over one-third of chemonaïve patients with G3 GEP-NENs, with a manageable safety profile.

Management of typical and atypical metastatic lung carcinoids: present and future perspectives

Lung carcinoids are rare tumors representing 1-2% of all invasive lung malignancies. They include typical and atypical carcinoids, whose distinction is made based on the mitotic index and presence or absence of necrosis. The 10-year overall survival for stage IV typical carcinoid is 47% and 18% for atypical carcinoid, reflecting the indolent growth of these tumors. There are limited approved treatment options for them and most of the evidence comes from retrospective analyses, single-arm trials, subgroup analysis of phase II/III trials for metastatic neuroendocrine tumors and extrapolation of data from phase III trials for gastroenteropancreatic neuroendocrine tumors. Management of metastatic lung carcinoids requires a multidisciplinary standardized approach in specialized centers. Treatment should have a dual objective, control of tumor growth and control of symptoms related to hypersecretion syndromes, aiming to improve quality of life and survival. In the continuum of treatment disease, locoregional treatment options need to be considered in parallel with systemic treatments. In this paper, we review the present treatment options and their rational and we give an insight into future alternatives.

Multimodal Treatment With Nivolumab Contributes to Long-Term Survival in a Case of Unresectable Esophagogastric Junction Neuroendocrine Carcinoma

Advanced neuroendocrine carcinoma (NEC) has an extremely poor prognosis, partly explained by the rarity and diagnostic difficulty, for which the most appropriate treatment strategy has not been established. In this report, we discuss a case of unresectable advanced esophagogastric junction NEC, which was difficult to diagnose, that has achieved relatively long-term survival with multidisciplinary treatment centered on nivolumab. A man in his 60s was initially diagnosed with an advanced esophagogastric junction squamous cell carcinoma (SCC). The lymph node metastasis was detected in the regional lymph nodes and para-aortic region. We diagnosed the patient with T3, N3, M1 (Lym), stage IVB, and administered systemic chemotherapy. Due to the failure of first-line, fluorouracil, and cisplatin therapy, we administered nivolumab as the second-line therapy. This therapy demonstrated partial response, so we performed conversion surgery, however the postoperative diagnosis was NEC. Three years after treatment initiation, a single lymph node metastasis has recurred, which is under control with nivolumab and radiation therapy. However, 4.5 years after the start of treatment, with the advent of immune-related adverse events (irAE), nivolumab was discontinued and the patient was placed on surveillance. Six months after that, metastasis to the hilar lymph node and adrenal gland was observed. Both times that recurrence/metastasis appeared, they occurred while nivolumab was being discontinued, suggesting its significant systemic anti-cancer effect. Therefore, nivolumab in particular may be an effective treatment for advanced esophageal NEC, and this case suggests that it may contribute to prolonged progression-free survival.

N-linked glycosylation of PD-L1/PD-1: an emerging target for cancer diagnosis and treatment

During tumorigenesis and progression, the immune checkpoint programmed death-1 (PD-1) and its ligand programmed death ligand-1 (PD-L1) play critical roles in suppressing T cell-mediated anticancer immune responses, leading to T-cell exhaustion and subsequent tumor evasion. Therefore, anti-PD-L1/PD-1 therapy has been an attractive strategy for treating cancer over the past decade. However, the overall efficacy of this approach remains suboptimal, revealing an urgent need for novel insights. Interestingly, increasing evidence indicates that both PD-L1 on tumor cells and PD-1 on tumor-specific T cells undergo extensive N-linked glycosylation, which is essential for the stability and interaction of these proteins, and this modification promotes tumor evasion. In various preclinical models, targeting the N-linked glycosylation of PD-L1/PD-1 was shown to significantly increase the efficacy of PD-L1/PD-1 blockade therapy. Furthermore, deglycosylation of PD-L1 strengthens the signal intensity in PD-L1 immunohistochemistry (IHC) assays, improving the diagnostic and therapeutic relevance of this protein. In this review, we provide an overview of the regulatory mechanisms underlying the N-linked glycosylation of PD-L1/PD-1 as well as the crucial role of N-linked glycosylation in PD-L1/PD-1-mediated immune evasion. In addition, we highlight the promising implications of targeting the N-linked glycosylation of PD-L1/PD-1 in the clinical diagnosis and treatment of cancer. Our review identifies knowledge gaps and sheds new light on the cancer research field.

Immunotherapy in Neuroendocrine Neoplasms: A Diamond to Cut

A raise in the incidence of NENs is expected. Therefore, the identification of new therapeutic strategies, such as immunotherapy, remains crucial. To date, immune checkpoint inhibitors as monotherapy have shown modest activity in unselected NENs. Although immunotherapy combos (plus another immune agents or chemotherapy, among others) are potentially more active than single agents, this has not been uniformly confirmed, even in high-grade NENs. Other immunotherapeutic strategies under development include bispecific antibodies, targeting specific tumor antigens like DLL3, and cell therapy. Currently, no predictive immune biomarkers are available to guide clinical decisions. A comprehensive tumor molecular profiling approach needs to be developed for the selection of patients with NEN who could potentially benefit from immunotherapy. Ideally, clinical trials should incorporate this tumor molecular profiling to identify predictive biomarkers and improve efficacy. Achieving this goal requires an international collaborative effort.

The Immune Landscape of Pheochromocytoma and Paraganglioma: Current Advances and Perspectives

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from neural crest cells from adrenal medullary chromaffin tissues and extra-adrenal paraganglia, respectively. Although the current treatment for PPGLs is surgery, optimal treatment options for advanced and metastatic cases have been limited. Hence, understanding the role of the immune system in PPGL tumorigenesis can provide essential knowledge for the development of better therapeutic and tumor management strategies, especially for those with advanced and metastatic PPGLs. The first part of this review outlines the fundamental principles of the immune system and tumor microenvironment, and their role in cancer immunoediting, particularly emphasizing PPGLs. We focus on how the unique pathophysiology of PPGLs, such as their high molecular, biochemical, and imaging heterogeneity and production of several oncometabolites, creates a tumor-specific microenvironment and immunologically "cold" tumors. Thereafter, we discuss recently published studies related to the reclustering of PPGLs based on their immune signature. The second part of this review discusses future perspectives in PPGL management, including immunodiagnostic and promising immunotherapeutic approaches for converting "cold" tumors into immunologically active or "hot" tumors known for their better immunotherapy response and patient outcomes. Special emphasis is placed on potent immune-related imaging strategies and immune signatures that could be used for the reclassification, prognostication, and management of these tumors to improve patient care and prognosis. Furthermore, we introduce currently available immunotherapies and their possible combinations with other available therapies as an emerging treatment for PPGLs that targets hostile tumor environments.

Gastroenteropancreatic neuroendocrine neoplasms: current development, challenges, and clinical perspectives

Neuroendocrine neoplasms (NENs) are highly heterogeneous and potentially malignant tumors arising from secretory cells of the neuroendocrine system. Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are the most common subtype of NENs. Historically, GEP-NENs have been regarded as infrequent and slow-growing malignancies; however, recent data have demonstrated that the worldwide prevalence and incidence of GEP-NENs have increased exponentially over the last three decades. In addition, an increasing number of studies have proven that GEP-NENs result in a limited life expectancy. These findings suggested that the natural biology of GEP-NENs is more aggressive than commonly assumed. Therefore, there is an urgent need for advanced researches focusing on the diagnosis and management of patients with GEP-NENs. In this review, we have summarized the limitations and recent advancements in our comprehension of the epidemiology, clinical presentations, pathology, molecular biology, diagnosis, and treatment of GEP-NETs to identify factors contributing to delays in diagnosis and timely treatment of these patients.

Emerging Treatment Options for Neuroendocrine Neoplasms of Unknown Primary Origin: Current Evidence and Future Perspectives

Among neuroendocrine neoplasms (NENs), a non-negligible proportion (9-22%) is represented by sufferers of NENs of unknown primary origin (UPO), a poor prognostic group with largely unmet clinical needs. In the absence of standard therapeutic algorithms, current guidelines suggest that the treatment of UPO-NENs should be based on tumor clinical-pathological characteristics, disease burden, and patient conditions. Chemotherapy represents the backbone for the treatment of high-grade poorly differentiated UPO-NENs, usually providing deep but short-lasting responses. Conversely, the spectrum of available systemic therapy options for well-differentiated UPO-NENs may range from somatostatin analogs in indolent low-grade tumors, to peptide receptor radioligand therapy, tyrosine kinase inhibitors (TKIs), or chemotherapy for more aggressive tumors or in case of high disease burden. In recent years, molecular profiling has provided deep insights into the molecular landscape of UPO-NENs, with both diagnostic and therapeutic implications. Although preliminary, interesting activity data have been provided about upfront chemoimmunotherapy, the use of immune checkpoint inhibitors (ICIs), and the combination of ICIs plus TKIs in this setting. Here, we review the literature from the last 30 years to examine the available evidence about the treatment of UPO-NENs, with a particular focus on future perspectives, including the expanding scenario of targeted agents in this setting.

ETV6-NTRK2 Fusion in a Patient With Metastatic Pulmonary Atypical Carcinoid Successfully Treated With Entrectinib: A Case Report and Review of the Literature

Pulmonary atypical carcinoid (AC) is an extremely rare neuroendocrine tumor. The neurotrophic tropomyosin receptor kinase (NTRK) fusions are reported in only 0.5% of nonsmall cell lung cancer, and are more rare in AC with only one previously reported case. Currently, there is little established evidence on the optimal therapeutic strategies and prognosis for advanced cases. We present a female patient with metastatic AC after complete resection. Due to low expression of somatostatin receptor in this case, somatostatin analogs and peptide receptor radionuclide therapy were not available. After pursuing other alternative treatments, including chemotherapy (ie, carboplatin, etoposide, capecitabine, temozolomide, and paclitaxel), everolimus, and atezolizumab, she returned with significant progression, including innumerable subcutaneous nodules, left pleura metastasis, multiple bone metastases, and brain metastases. New biopsy analysis revealed an ETV6-NTRK2 fusion. She was immediately administered the first-generation tropomyosin receptor kinase inhibitor entrectinib at a dose of 600 mg q.d. A subsequent month of treatment resulted in a complete response in all of the metastatic lung lesions. To date, she has maintained sustained benefit for at least 1 year from initiation of entrectinib. Here, we present the first case of a female patient with metastatic AC harboring the ETV6-NTRK2 fusion, and successfully treated with entrectinib, providing evidence for the application of entrectinib in patients with NTRK-positive AC, and underscoring the critical role of molecular profiling for such cases.

Extrapulmonary Neuroendocrine Carcinomas: Current Management and Future Perspectives

Neuroendocrine carcinomas (NECs) are poorly differentiated and highly aggressive epithelial neuroendocrine neoplasms. The most common primary site is the lung, but they may arise in every organ. Approximately 37% of extrapulmonary NECs (EP-NECs) occur in the gastroenteropancreatic (GEP) tract, followed by the genitourinary (GU) system and gynecological tract. As a result of their rarity, there is scant evidence to guide treatment recommendations, and a multidisciplinary approach is essential for the management of such patients. Platinum-based chemotherapy currently represents the standard of care for EP-NECs of any site, mirroring the management of small-cell lung cancer (SCLC), but further approaches are still under investigation. Indeed, ongoing trials evaluating targeted therapies, immune checkpoint inhibitors (ICIs), and radionuclide therapy could provide potentially breakthrough therapeutic options. Given the relative dearth of evidence-based literature on these orphan diseases, the aim of this review is to provide an overview of the pathology and current treatment options, as well as to shed light on the most pressing unmet needs in the field.

Narrative Review of Immunotherapy in Gastroentero-Pancreatic Neuroendocrine Neoplasms

Gastroentero-pancreatic Neuroendocrine Neoplasms (GEP-NENs) are a diverse group of rare tumors that arise from neuroendocrine cells in the gastrointestinal tract and pancreas, and they can vary significantly in terms of clinical behavior and prognosis. Immunotherapy, particularly immune checkpoint inhibitors, has shown remarkable success in various malignancies by harnessing the body's immune system to target and eliminate cancer cells. Immune checkpoint inhibitor clinical studies in GEP-NENs have yielded promising outcomes, particularly in individuals with advanced and refractory disease. Objective responses and disease stabilization have been observed in some cases, even in those previously unresponsive to traditional treatments like chemotherapy or targeted therapies. However, it's important to note that the efficacy of immunotherapy in GEP-NENs can vary widely depending on tumor characteristics, the immune microenvironment, and patient factors. As such, identifying predictive biomarkers to select the most suitable patients for immunotherapy remains an ongoing challenge. Immunotherapy has considerable potential for treating GEP-NENs, but research is still in its early stages. Several combinations are being explored to enhance the effectiveness of immunotherapy and improve the outcomes of treatment, such as combining immunotherapy with other targeted therapies or chemotherapy.

Expert Consensus Practice Recommendations of the North American Neuroendocrine Tumor Society for the management of high grade gastroenteropancreatic and gynecologic neuroendocrine neoplasms

High-grade neuroendocrine neoplasms are a rare disease entity and account for approximately 10% of all neuroendocrine neoplasms. Because of their rarity, there is an overall lack of prospectively collected data available to advise practitioners as to how best to manage these patients. As a result, best practices are largely based on expert opinion. Recently, a distinction was made between well-differentiated high-grade (G3) neuroendocrine tumors and poorly differentiated neuroendocrine carcinomas, and with this, pathologic details, appropriate imaging practices and treatment have become more complex. In an effort to provide practitioners with the best guidance for the management of patients with high-grade neuroendocrine neoplasms of the gastrointestinal tract, pancreas, and gynecologic system, the North American Neuroendocrine Tumor Society convened a panel of experts to develop a set of recommendations and a treatment algorithm that may be used by practitioners for the care of these patients. Here, we provide consensus recommendations from the panel on pathology, imaging practices, management of localized disease, management of metastatic disease and surveillance and draw key distinctions as to the approach that should be utilized in patients with well-differentiated G3 neuroendocrine tumors vs poorly differentiated neuroendocrine carcinomas.