Gastroenteropancreatic grade 3 neuroendocrine tumors: a single entity or a heterogeneous group? A retrospective analysis

Targeting neuroendocrine tumors with octreotide and lanreotide: Key points for clinical practice from NET specialists

Octreotide and lanreotide are the two somatostatin analogs (SSA) currently available in clinical practice. They have been approved first to control the clinical syndrome (mainly carcinoid syndrome) associated with functioning neuroendocrine tumors (NET) and later for tumor growth control in advanced low/intermediate grade NET. Although evidence regarding their role, especially as antiproliferative therapy, has been increasing over the years some clinical indications remain controversial. Solicited by AIOM (Italian Association of Medical Oncology) a group of clinicians from various specialties, including medical oncology, endocrinology, and gastroenterology, deeply involved in NET for their clinical and research activity, addressed eight open questions, critically reviewing evidence and guidelines and sharing clinical take-home messages. The questions regarded the use of long-acting octreotide and lanreotide in the following settings: functioning and non-functioning NET refractory to label dose, first-line metastatic pulmonary NET, combination with other therapy with an antiproliferative intent, maintenance in NET responding to other therapies, adjuvant treatment, Ki-67-related cut-off, somatostatin receptor imaging, safety, and feasibility. The level of evidence is not absolute for the majority of these clinical contexts, so it is recommended to distinguish routine versus sporadic utilization in very selected cases. Mention of such specific issues by the main European guidelines (ENETS, European Neuroendocrine Tumor Society, and ESMO, European Society for Medical Oncology) was explored and their position reported. However, different clinical decisions on single patients could be made if the case is carefully discussed within a NET-dedicated multidisciplinary team.

Tumour Heterogeneity and the Consequent Practical Challenges in the Management of Gastroenteropancreatic Neuroendocrine Neoplasms

Tumour heterogeneity is a common phenomenon in neuroendocrine neoplasms (NENs) and a significant cause of treatment failure and disease progression. Genetic and epigenetic instability, along with proliferation of cancer stem cells and alterations in the tumour microenvironment, manifest as intra-tumoural variability in tumour biology in primary tumours and metastases. This may change over time, especially under selective pressure during treatment. The gastroenteropancreatic (GEP) tract is the most common site for NENs, and their diagnosis and treatment depends on the specific characteristics of the disease, in particular proliferation activity, expression of somatostatin receptors and grading. Somatostatin receptor expression has a major role in the diagnosis and treatment of GEP-NENs, while Ki-67 is also a valuable prognostic marker. Intra- and inter-tumour heterogeneity in GEP-NENS, however, may lead to inaccurate assessment of the disease and affect the reliability of the available diagnostic, prognostic and predictive tests. In this review, we summarise the current available evidence of the impact of tumour heterogeneity on tumour diagnosis and treatment of GEP-NENs. Understanding and accurately measuring tumour heterogeneity could better inform clinical decision making in NENs.

A systematic review of therapeutic strategies in gastroenteropancreatic grade 3 neuroendocrine tumors

Background

Gastroenteropancreatic (GEP) neuroendocrine neoplasms with Ki-67 > 20% were subdivided in the most recent 2019 World Health Organization histopathological classification into grade 3 (G3) neuroendocrine tumors (NETs), described as well-differentiated tumors, and neuroendocrine carcinomas, which are described as poorly differentiated tumors. This classification met the demand noted for different prognoses between these subgroups, prompting the need for treatment recommendations for well-differentiated G3 tumors.

Methods

We systematically searched medical literature databases and oncology conferences for studies on G3 GEP NET to describe epidemiology, diagnosis, molecular features, and treatments used. We excluded studies that did not discriminate G3 NET data. Data were tabulated and described, and a quality analysis of the reports was performed.

Results

We found 23 published studies and six abstracts; 89.7% of studies were retrospective, six were composed exclusively of G3 NETs. Among 761 patients, the median number of patients per study was 15, most were male and older than 60 years, and functional imaging tests were positive in more than 80% of cases. Overall, the scientific evidence supporting the treatment of G3 GEP NETs is limited. For localized disease, resection remains the standard treatment but there is no evidence to support neoadjuvant or adjuvant therapy. For advanced disease, capecitabine and temozolomide seems to be the most effective option, with a response rate, median progression-free survival, and median overall survival up to 37.9%, 20.6 months, and 41.2 months, respectively.

Conclusion

The latest available data on the epidemiology, diagnosis, molecular changes, and treatment of G3 GEP NET are described. Yet, the level of evidence for treatment recommendations is low, as most studies are retrospective. A treatment algorithm for G3 GEP NET is proposed.

DLL3 as an Emerging Target for the Treatment of Neuroendocrine Neoplasms

INTRODUCTION

Neuroendocrine neoplasms (NEN) are heterogeneous malignancies that can arise at almost any anatomical site and are classified as biologically distinct well-differentiated neuroendocrine tumors (NET) and poorly differentiated neuroendocrine carcinomas (NEC). Current systemic therapies for advanced disease, including targeted therapies, chemotherapy, and immunotherapy, are associated with limited duration of response. New therapeutic targets are needed. One promising target is delta-like ligand 3 (DLL3), an inhibitory ligand of the Notch receptor whose overexpression on the surface of NEN is associated with tumorigenesis.

METHODS

This article is a narrative review that highlights the role of DLL3 in NEN progression and prognosis, the potential for therapeutic targeting of DLL3, and ongoing studies of DLL3-targeting therapies. Classification, incidence, pathogenesis, and current management of NEN are reviewed to provide biological context and illustrate the unmet clinical needs.

DISCUSSION

DLL3 is overexpressed in many NENs, implicated in tumor progression, and is typically associated with poor clinical outcomes, particularly in patients with NEC. Targeted therapies using DLL3 as a homing beacon for cytotoxic activity mediated via several different mechanisms (eg, antibody-drug conjugates, T-cell engager molecules, CAR-Ts) have shown promising clinical activity in small-cell lung cancer (SCLC). DLL3 may be a clinically actionable target across NEN.

CONCLUSIONS

Current treatment options for NEN do not provide sustained responses. DLL3 is expressed on the cell surface of many NEN types and is associated with poor clinical outcomes. Initial clinical studies targeting DLL3 therapeutically in SCLC have been promising, and additional studies are expanding this approach to the broader group of NEN.

Clinicopathological and molecular profile of grade 3 gastroenteropancreatic neuroendocrine neoplasms

The 2019 Word Health Organization (WHO) subclassified grade 3 (G3) gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN) into neuroendocrine carcinoma (NEC) or tumours (G3 NET) based on morphology and proliferation. Yet, few data exist on molecular profiles for G3 NEN. We compared clinicopathological and molecular characteristics of these two groups. We retrospectively reviewed consecutive G3 GEP NEN patients and had their tumour tissues reviewed, reclassified as per the WHO 2019, and analyzed by a next-generation sequencing (NGS) panel. Between 2000 and 2019, 43 patients had pathology revision: 29 (67%) were NEC and 14 (33%) were G3 NET, with a 23% change in diagnosis. Median overal survival for G3 NET and NEC patients was 55.6 and 11.9 months, respectively (hazard ratio = 2.78 [95% confidence interval = 1.09-7.11], p = .042), which was confirmed by an adjusted analysis (hazard ratio = 2.90 NEC vs. G3 NET; p = .03). NGS was performed in 32 cases: 21 NEC and 11 G3 NET. Mutations in RB1 and PTEN were exclusively encountered in NEC. Median tumour mutational burden was 5 (0-67) mutations per megabase in NEC and 4.5 (0-9) among G3 NET. Microsatellite instability was found in 3 (14.3%) NEC cases. In conclusion, pathology revision is essential to estimate prognosis and therapeutic plan. G3 GEP NEN generally harbour low tumor mutation burden and fewer actionable mutations, but 14% of NEC cases were microsatellite unstable and could benefit from immune checkpoint inhibitors.

A Retrospective Analysis of the Correlation between Functional Imaging and Clinical Outcomes in Grade 3 Neuroendocrine Tumors (NETs G3)

Grade 3 (G3) neuroendocrine tumors (NETs) are a novel category among digestive neuroendocrine neoplasms, characterized by Ki-67 >20% and a well-differentiated morphology, presenting high intra-tumor heterogeneity. We aimed to explore the role of dual-tracer PET imaging (68Gallium (Ga)-DOTATOC and 18Fluorodeoxyglucose (FDG)) as overall survival (OS) predictor in NET G3 patients. We performed a retrospective analysis in NET G3 patients treated at our institution between 2003 and 2021. Accordingly, 30 NET G3 patients were analyzed. 68Ga-DOTA-TOC and 18F-FDG uptake were assessed by tumor/non-tumor (T-nonT) ratio. We reported a slightly better OS for patients with ≥75% concordance between 68Ga-DOTA-TOC and 18F-FDG PET/CT (p = 0.42). Among patients with discordant functional imaging, we reported a better 5-y OS rate for patients with a prevalent 68Ga-DOTATOC vs. 18F-FDG PET/CT (p = 0.016). In positive 18F-FDG PET/CT cases, we reported a better OS for <4 vs. ≥4 T/non-T ratio (p = 0.021). Among upfront-NET G3 patients with concordant exams, 5-y OS rate was 83.3% (95% CI: 27.3-97.5). Among patients with discordant exams, 5-y OS rate was 81.3% (52.5-93.5), 100% for those with prevalent receptor expression, and 50% (11.1-80.4) for those with prevalent 18F-FDG uptake. Our findings suggest that dual-tracer PET/CT can be considered as a predictor of patient outcome, able to stratify NET G3 patients with poorer prognosis.

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.