Extremely Long Survival under Combined Immunotherapy in a Metastatic Functional Neuroendocrine Neoplasia Patient

Gastric Neuroendocrine Tumors (g-NETs): A Systematic Review of the Management and Outcomes of Type 3 g-NETs

PURPOSE

to collect data from real-life experiences of the management of type 3 g-NETs and identify possible prognostic factors that may impact the decision-making process.

METHODS

We performed a systematic review of the literature on type 3 g-NET management using the PubMed, MEDLINE, and Embase databases. We included cohort studies, case series, and case reports written in the English language.

RESULTS

We selected 31 out of 556 articles from between 2001 and 2022. In 2 out of the 31 studies, a 10 mm and 20 mm cut-off size were respectively associated with a higher risk of gastric wall infiltration and/or lymph node and distant metastasis at diagnosis. The selected studies reported a higher risk of lymph node or distant metastasis at diagnosis in the case of muscularis propria infiltration or beyond, irrespective of the dimensions or grading. From these findings, size, grading, and gastric wall infiltration seem to be the most relevant factors in management staff making choices and prognoses of type 3 g-NET patients. We produced a hypothetical flowchart for a standardized approach to these rare diseases.

CONCLUSION

Further prospective analyses are needed to validate the prognostic impact of the use of size, grading, and gastric wall infiltration as prognostic factors in the management of type 3 g-NETs.

Gastroenteropancreatic neuroendocrine neoplasms G3: Novel insights and unmet needs

According to the 2019 WHO pathology grading system, high-grade gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) can be divided into well differentiated neuroendocrine tumors G3 (NETs G3) and poorly differentiated neuroendocrine carcinomas (NECs). GEP-NETs G3 and GEP-NECs present significant differences in driver genes and disease origin. NETs G3 and NECs have been confirmed to be two distinct diseases with different genetic backgrounds, however, this issue remains controversial. The prognosis of NETs G3 is significantly better than that of NECs. The differential diagnosis of GEP-NETs G3 and GEP-NECs should be combined with the patient's medical history, tumor histopathology, Ki-67 index, DAXX/ATRX, TP53 and Rb expression as well as other immunohistochemical indicators. In addition, the treatment strategies of these two subgroups are very different. Here, we summarize recent findings focused on the genomics, clinical manifestations, diagnosis, treatment and other aspects of high-grade GEP-NENs (G3). This review may help further our understanding of the carcinogenesis, diagnosis and treatment of GEP-NENs G3.

Role of immunotherapy in gastro-enteropancreatic neuroendocrine neoplasms (gep-nens): Current advances and future directions

Neuroendocrine neoplasms (NENs) are heterogeneous tumours originating from neuroendocrine cells (Pearse & Polak, Gut, 1971, 12,783). They were once considered as rare tumours, although their annual incidence has increased significantly and now exceeds seven cases in 100 000 in the USA (Dasari, et al., JAMA oncology, 2017, 3, 1335). They are a group of highly diverse neoplasms and can be classified into the spectrum of well-differentiated neuroendocrine tumours to poorly differentiated neuroendocrine carcinomas. This is entirely based on the tumour differentiation and grade (low, intermediate, high), which is determined by the Ki-67/mitotic index. The lower grades (G1/2) of the well-differentiated group are characterised by a relative indolent clinical course and the ability to secrete a variety of peptide hormones (Kloppel, Visceral medicine, 2017, 33, 324). Higher grades and poorly differentiated tumours tend to be more aggressive and have limited therapeutic options (Sorbye et al., Neuroendocrinology, 2019, 108, 54). In the modern era of immuno-oncology, immune checkpoint inhibitors (ICPIs) that target programmed cell death 1 (pembrolizumab, nivolumab), programmed cell death-ligand1 (avelumab, atezolizumab and durvalumab) or cytotoxic T-lymphocyte-associated protein 4 (ipilimumab) have revolutionised the management of many solid tumours. In patients with gastro-enteropancreatic (GEP)-NENs, there is a limited data regarding the role of ICPIs either as a single agent or in combination regimens. Here, we review the current advances for ICPIs and where they fit in the management of GEP-NENs.

PD-L1 - inhibitors in neuroendocrine neoplasia: Results from a real-life study

Immune check-point inhibitors (ICIs) have changed our view on how to treat cancer. Despite their approval in treatment of many different cancers, efficacy of immune check-point inhibitors (ICI) in neuroendocrine neoplasia is limited and poorly understood. Established treatment options of neuroendocrine tumors (NET) and neuroendocrine carcinomas (NECs) are based on surgery, tumor-targeted medical treatments, Peptide Receptor Radionuclide Therapy (PRRT), and locoregional therapies. However, in many patients these treatments lose efficacy over time, and novel therapies are urgently needed. We report on 8 patients diagnosed with neuroendocrine neoplasms (NEN) that were treated with ICI (pembrolizumab, avelumab, nivolumab plus ipilimumab) as salvage therapy. In this cohort, we observed tumor response with partial remission in 3 patients and stable disease in 1 patient. Four patients showed progressive disease. Of note, responses were observed both in PD-L1 positive and PD-L1 negative patients. Here, we discuss clinical courses of these patients in the context of available literature to highlight limitations and drawbacks currently preventing the use of ICI in routine management of patients with NEN.

Neuroendocrine neoplasia of the gastrointestinal tract revisited: towards precision medicine

Over the past 5 years, a number of notable research advances have been made in the field of neuroendocrine cancer, specifically with regard to neuroendocrine cancer of the gastrointestinal tract. The aim of this Review is to provide an update on current knowledge that has proven effective for the clinical management of patients with these tumours. For example, for the first time in the tubular gastrointestinal tract, well-differentiated high-grade (grade 3) tumours and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) are defined in the WHO classification. This novel classification enables efficient identification of the most aggressive well-differentiated neuroendocrine tumours and helps in defining the degree of aggressiveness of MiNENs. The Review also discusses updates to epidemiology, cell biology (including vesicle-specific components) and the as-yet-unresolved complex genetic background that varies according to site and differentiation status. The Review summarizes novel diagnostic instruments, including molecules associated with the secretory machinery, novel radiological approaches (including pattern recognition techniques), novel PET tracers and liquid biopsy combined with DNA or RNA assays. Surgery remains the treatment mainstay; however, peptide receptor radionuclide therapy with novel radioligands and new emerging medical therapies (including vaccination and immunotherapy) are evolving and being tested in clinical trials, which are summarized and critically reviewed here.

Landscape and Future Perspectives of Immunotherapy in Neuroendocrine Neoplasia

BACKGROUND

Neuroendocrine neoplasms are rare entities consisting of a heterogeneous group of tumors that can originate from neuroendocrine cells present in the whole body. Their different behavior, metastatic potential, and prognosis are highly variable, depending on site of origin, grade of differentiation, and proliferative index. The aim of our work is to summarize the current knowledge of immunotherapy in different neuroendocrine neoplasms and its implication in clinical practice.

RESULTS

Several studies evaluated the efficacy and safety of immunotherapy in neuroendocrine neoplasms, in any setting of treatment, alone or in combination. Studies led to approval in neuroendocrine neoplasia of the lung, in combination with chemotherapy as first-line treatment or as a single-agent in a third-line setting, and Merkel cell carcinoma as a single agent. Results in other settings have been disappointing so far.

CONCLUSIONS

Immunotherapy seems a valid treatment option for high grade, poorly differentiated neoplasms. Future trials should explore the combination of immunotherapy with other agents, such as anti-angiogenic or other immunotherapy agents, in order to evaluate potential efficacy in low and intermediate grades, well differentiated tumors.

The tumor immune microenvironment in gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are a group of rare tumors that are increasing in prevalence. The complex tumor immune microenvironment (TIME) plays an important role in tumor development and the response to immunotherapy but is poorly understood. In this review, the components of the TIME are described in detail, including discussion about infiltrating immune cells, the immune checkpoint system, the cytokine and chemokine milieu, and immunomodulatory factors. Moreover, a comparison between TIMEs among different types of GEP-NENs and the interplay among the TIME, tumor cells, and the stromal microenvironment is described. Novel treatment options for GEP-NENs and potential biomarkers for the immune response are also characterized. We provide a comprehensive generalized review of the TIME that can inform GEP-NEN treatment strategies.

Sustained partial remission of a metastatic NEN using off-label immunotherapy with pembrolizumab

Neuroendocrine neoplasms (NEN) are a heterogeneous group of tumors, which can be histologically separated by primary location, proliferation rate and differentiation of tumor cells. The therapeutic options and outcome depend on grading, staging and resectability of the tumor. Established treatment options of neuroendocrine tumors (NET) and carcinomas (NEC) are based especially on surgery, tumor specific medical treatments, peptide guided radioreceptor therapy (PRRT) and locoregional therapies. We report about a patient diagnosed with a pancreatic, non-functional NET/NEC G2/3 with a proliferation rate of 20% at initial immunohistochemical diagnosis. During the course of the disease, the proliferation rate increased up to more than 50% over a period of 5 years. Due to loss of response to established therapies (i.e. systemic chemotherapy, targeted therapy and brachytherapy), an off-label immunotherapy with the PD-1 antibody pembrolizumab was initiated based on a 30% PD-L1 expression in tumor cells. This report is the first demonstrating a partial remission of a pancreatic NEN using pembrolizumab monotherapy with a hepatic tumor volume reduction of at least 66%, combined with an improvement of the Karnofsky score rising from 60% to 100%. This case offers insight into the potential role of immunotherapy in a subgroup of neuroendocrine neoplasms.

The Tumor Microenvironment in Neuroendocrine Tumors: Biology and Therapeutic Implications

Neuroendocrine tumors (NETs) include a heterogeneous group of malignancies arising in the diffuse neuroendocrine system and characterized by indolent growth. Complex interactions take place among the cellular components of the microenvironment of these tumors, and the recognition of the molecular mediators of their interplay and cross talk is crucial to discover novel therapeutic targets. NET cells overexpress a plethora of proangiogenic molecules including vascular endothelial growth factor, platelet-derived growth factor, fibroblast growth factor, semaphorins, and angiopoietins that promote both recruitment and proliferation of endothelial cell precursors, thus resulting among the most vascularized cancers with a microvessel density 10-fold higher than epithelial tumors. Also, NETs operate multifaceted interactions with stromal cells, both at local and distant sites, and whether their paracrine secretion of serotonin, connective tissue growth factor, and transforming growth factor β primarily drives the fibroblast activation to enhance the tumor proliferation, on the other side NET-derived profibrotic factors accelerate the extracellular matrix remodeling and contribute to heart valves and/or mesenteric fibrosis development, namely, major complications of functioning NETs. However, at present, little is known on the immune landscape of NETs, but accumulating evidence shows that tumor-infiltrating neutrophils, mast cells, and/or macrophages concur to promote the neoangiogenic switch of these tumors by either direct or indirect mechanisms. On the other hand, immune checkpoint molecules are heterogeneously expressed in NETs' surrounding cells, and it is unclear whether or not tumor-infiltrating lymphocytes are antitumor armed within the microenvironment, given their low mutational load. Here, we review the current knowledge on both gastroenteropancreatic and pulmonary NETs' microenvironment as well as both established and innovative treatments aimed at targeting the tumor-host interplay.