Improving the diagnosis and management of neuroendocrine tumors: utilizing new advances in biomarker and molecular imaging science

PCDHGC3 hypermethylation as a potential biomarker of intestinal neuroendocrine carcinomas

Neuroendocrine neoplasms (NENs) encompass tumors arising from neuroendocrine cells in various organs, including the gastrointestinal tract, pancreas, adrenal gland, and paraganglia. Despite advancements, accurately predicting the aggressiveness of gastroenteropancreatic (GEP) NENs based solely on pathological data remains challenging, thereby limiting optimal clinical management. Our previous research unveiled a crucial link between hypermethylation of the protocadherin PCDHGC3 gene and neuroendocrine tumors originating from the paraganglia and adrenal medulla. This epigenetic alteration was associated with increased metastatic potential and succinate dehydrogenase complex (SDH) dysfunction. Expanding upon this discovery, the current study explored PCDHGC3 gene methylation within the context of GEP-NENs in a cohort comprising 34 cases. We uncovered promoter hypermethylation of PCDHGC3 in 29% of GEP-NENs, with a significantly higher prevalence in gastrointestinal (GI) neuroendocrine carcinomas (NECs) compared with both pancreatic (Pan) NECs and neuroendocrine tumors (NETs) of GI and Pan origin. Importantly, these findings were validated in one of the largest multi-center GEP-NEN cohorts. Mechanistic analysis revealed that PCDHGC3 hypermethylation was not associated with SDH mutations or protein loss, indicating an SDH-independent epigenetic mechanism. Clinically, PCDHGC3 hypermethylation emerged as a significant prognostic factor, correlating with reduced overall survival rates in both patient cohorts. Significantly, whereas PCDHGC3 hypermethylation exhibited a strong correlation with TP53 somatic mutations, a hallmark of NEC, its predictive value surpassed that of TP53 mutations, with an area under the curve (AUC) of 0.95 (95% CI 0.83-1.0) for discriminating GI-NECs from GI-NETs, highlighting its superior predictive performance. In conclusion, our findings position PCDHGC3 methylation status as a promising molecular biomarker for effectively stratifying patients with GI-NENs. This discovery has the potential to advance patient care by enabling more precise risk assessments and tailored treatment strategies. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Multimodal management of foregut neuroendocrine neoplasms

The foregut, which includes the esophagus, stomach and duodenum, represents one of the most common sites for neuroendocrine neoplasms. These are highly heterogenous with different risk of progression depending on location, cell-type of origin, size, grade and other factors. Various endoscopic and imaging modalities exist to inform therapeutic decision-making, which may be in the form of surgical or endoscopic resection and medical therapy depending on the extent of the disease after diagnostic evaluation. This narrative review aims to explore the literature on the multimodal management of such foregut neuroendocrine neoplasms.

Virus-associated neuroendocrine cancers: Pathogenesis and current therapeutics

Neuroendocrine neoplasms (NENs) comprise malignancies involving neuroendocrine cells that often lead to fatal pathological conditions. Despite escalating global incidences, NENs still have poor prognoses. Interestingly, research indicates an intricate association of tumor viruses with NENs. However, there is a dearth of comprehension of the complete scenario of NEN pathophysiology and its precise connections with the tumor viruses. Interestingly, several cutting-edge experiments became helpful for further screening of NET for the presence of polyomavirus, Human papillomavirus (HPV), Kaposi sarcoma-associated herpesvirus (KSHV), Epstein Barr virus (EBV), etc. Current research on the neuroendocrine tumor (NET) pathogenesis provides new information concerning their molecular mechanisms and therapeutic interventions. Of note, scientists observed that metastatic neuroendocrine tumors still have a poor prognosis with a palliative situation. Different oncolytic vector has already demonstrated excellent efficacies in clinical studies. Therefore, oncolytic virotherapy or virus-based immunotherapy could be an emerging and novel therapeutic intervention. In-depth understanding of all such various aspects will aid in managing, developing early detection assays, and establishing targeted therapeutic interventions for NENs concerning tumor viruses. Hence, this review takes a novel approach to discuss the dual role of tumor viruses in association with NENs' pathophysiology as well as its potential therapeutic interventions.

The Role of Conventionally Fractionated Radiotherapy and Stereotactic Radiotherapy in the Treatment of Carcinoid Tumors and Large-Cell Neuroendocrine Cancer of the Lung

The occurrence of neuroendocrine tumors among the diagnosed neoplasms is extremely rare and is associated with difficulties in undertaking effective therapy due to the histopathological differentiation of individual subtypes and the scarce clinical data and recommendations found in the literature. The choice of treatment largely depends not only on its type, but also on the location and production of excess hormones by the tumor itself. Common therapeutic approaches include surgical removal of the tumor, the use of chemotherapy, targeted drug therapy, peptide receptor radionuclide therapy, and the use of radiation therapy. This article reviews the current knowledge on the classification and application of radiotherapy in the treatment of lung NETs. Case reports were presented in which treatment with conventional radiotherapy, radical and palliative radiochemotherapy, as well as stereotactic fractionated radiotherapy in the treatment of typical (TC) and atypical (AT) lung carcinoids and large cell neuroendocrine carcinoma (LCNC) were used. We hope that the solutions presented in the literature will allow many radiation oncologists to make the best, often personalized decisions about the therapeutic qualifications of patients.

Hypoglycemia and seizures associated with canine primary hepatic neuroendocrine carcinoma

A 10-y-old intact male Labrador Retriever dog had a history of ataxia, inability to stand, and grand mal seizures. Complete blood count and serum biochemistry profiles revealed profound hypoglycemia, mildly increased alanine aminotransferase (ALT) activity, mild hypernatremia, and lymphopenia. The seizures could not be controlled with intravenous dextrose, diazepam, or propofol. The dog was euthanized given poor quality of life, and an autopsy was performed. Primary autopsy findings included firm hepatic masses that ranged from dark-red to tan, with the largest ~1.5 cm diameter, and pulmonary edema. Histologic examination of the hepatic masses revealed redundant, several-cell-thick cords, and packeted or acinar arrangements of polygonal cells, supported on a fibrovascular stroma. The neoplastic cells were immunopositive for insulin, synaptophysin, and neuron-specific enolase immunohistochemistry; granules in the tumor cells had an affinity for Grimelius silver stain. The histologic features, as well as the immunohistochemical staining profile, identified the neoplasm as a primary multifocal hepatic neuroendocrine carcinoma. Neuroendocrine carcinomas are rare in dogs and usually occur in the gastrointestinal or respiratory tract.

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.

Circulating Transcript Analysis (NETest) in GEP-NETs Treated With Somatostatin Analogs Defines Therapy

CONTEXT

Early and precise delineation of therapeutic responses are key issues in neuroendocrine neoplasm/tumor management. Imaging is currently used but exhibits limitations in sensitivity and specificity. The utility of biomarkers is unclear. objective, setting, and design: This prospective cohort study (11 mo) sought to determine whether measurements of circulating neuroendocrine tumor transcripts (NETest) predict responses to somatostatin analogs (SSAs).

PATIENTS

The test set consisted of 35 SSA-treated gastroenteropancreatic-NETs (RECISTevaluated). The prospective set consisted of 28 SSA-treated Grade 1-Grade 2 GEP-NETs.

INTERVENTION(S)

Whole blood for transcript analysis (NETest) and plasma for Chromogranin A (CgA) (baseline), were collected every 4 weeks (prior to SSA injection). Morphologic (multidetector computed tomography/MRI) and functional imaging ((99m)Tc-[HYNIC, Tyr(3)]-Octreotide) was undertaken at entry and 6-month intervals until progression (RECIST 1.0).

MAIN OUTCOME MEASURE(S)

Treatment response.

RESULTS

Test set: NETest (≥80%; scale, 0-100%) differentiated stable (SD) and progressive (PD) disease (P < .0001). Prospective set: 28 patients (26/28 SD) undergoing standard SSA. Grading: 12 G1, 16 G2. SSA Response: progression-free survival: 315 days: 14 (50%) SD, 14 (50%) PD. NETest: Twenty had elevated (≥80%) values; 14 developed PD; six, SD. CgA: Twelve of 28 exhibited elevated baseline values and/or subsequent >25% increase; eight developed PD; four, SD. NETest (P = .002) and grade (P = .054) were the only factors associated with treatment response. Multiple regression analysis established that the NETest could predict disease progression (P = .0002). NETest changes occurred significantly earlier (146 d prior to progression vs 56 d CgA; P < .0001; χ(2) = 19) and in more patients (100 vs 57%; P < .02).

CONCLUSIONS

NETest values (80-100%) were more accurate and occurred at a significantly earlier time point than CgA and predicted SSA treatment response.

The status of neuroendocrine tumor imaging: from darkness to light?

Diagnostic imaging plays a pivotal role in the diagnosis, staging, treatment selection and follow-up for neuroendocrine tumors. The available diagnostic strategies are morphologic imaging, including computed tomography, magnetic resonance imaging (MRI) and ultrasound techniques, and molecular imaging, including scintigraphy with (111)In-pentetreotide and positron emission tomography with (68)Ga-DOTA-peptides, (18)F-DOPA and (11)C-5-HTP. A combination of anatomic and functional techniques is routinely performed to optimize sensitivity and specificity. The introduction of diffusion-weighted MRI and dynamic contrast-enhanced techniques represents a promising advance in radiologic imaging, whereas new receptor-binding peptides, including somatostatin agonists and antagonists, represent the recent most favorable innovation in molecular imaging. Future development includes the short-term validation of these techniques, but in extension also a more comprehensive multilevel integration of biologic information pertaining to a specific tumor and patient, possibly encompassing genomic considerations, currently evolving as a new entity denoted 'precision medicine'. The ideal is a diagnostic sequence that captures the global status of an individual's tumor and encompasses a multidimensional characterization of tumor location, metabolic performance and target identification. To date, advances in imagery have focused on increasing resolution, discrimination and functional characterization. In the future, the fusion of imagery with the parallel analysis of biological and genomic information has the potential to considerably amplify diagnosis.

Blood transcript analysis and metastatic recurrent small bowel carcinoid management

Background

Detection of neuroendocrine tumor (NET) disease progression is a key issue in determining management. Currently, assessment is by imaging (MRI/CT and Octreoscan®) and plasma Chromogranin A (CgA) measurement.

Case presentation

We report use of a NET-specific multigene PCR-derived blood transcript signature (NET Index) to assess disease and correlated CgA and gene transcripts with MRI, CT, Octreoscan®, ¹¹C-5HTP-PET/CT and ⁶⁸Ga-DOTA-PET/CT in a patient with NET.

Conclusions

Our results identify limitations in evaluating disease status by CgA and identify that a PCR-based test is more sensitive. Alteration in NET blood gene transcript levels prior to image-based tumor confirmation suggests this parameter may also have utility as an index of therapeutic efficacy.

Classification, clinicopathologic features and treatment of gastric neuroendocrine tumors

Gastric neuroendocrine tumors (GNETs) are rare lesions characterized by hypergastrinemia that arise from enterochromaffin-like cells of the stomach. GNETs consist of a heterogeneous group of neoplasms comprising tumor types of varying pathogenesis, histomorphologic characteristics, and biological behavior. A classification system has been proposed that distinguishes four types of GNETs; the clinicopathological features of the tumor, its prognosis, and the patient’s survival strictly depend on this classification. Thus, correct management of patients with GNETs can only be proposed when the tumor has been classified by an accurate pathological and clinical evaluation of the patient. Recently developed cancer therapies such as inhibition of angiogenesis or molecular targeting of growth factor receptors have been used to treat GNETs, but the only definitive therapy is the complete resection of the tumor. Here we review the literature on GNETs, and summarize the classification, clinicopathological features (especially prognosis), clinical presentations and current practice of management of GNETs. We also present the latest findings on new gene markers for GNETs, and discuss the effective drugs developed for the diagnosis, prognosis and treatment of GNETs.

Hematological toxicity of combined 177Lu-octreotate radiopeptide chemotherapy of gastroenteropancreatic neuroendocrine tumors in long-term follow-up

BACKGROUND

The combination of radiopeptide therapy [peptide receptor radionuclide therapy (PRRT)] with radiosensitizing chemotherapy of gastroenteropancreatic neuroendocrine tumors (GEP NETs) may improve efficacy, but has the potential to increase myelotoxicity. In a prospective clinical study of GEP NET patients treated with (177)Lu-octreotate PRRT in combination with capecitabine and temozolomide, as a prelude to a planned Australasian Gastro-Intestinal Trials Group (AGITG) international randomized controlled trial, we characterized the incidence and degree of hematological toxicity.

MATERIALS AND METHODS

Well-differentiated progressive metastatic GEP NETs in 65 patients were treated with 4 cycles of 7.8 GBq (177)Lu-octreotate, 1,650 mg/m(2) capecitabine (n = 28) and 1,500 mg/m(2) capecitabine with 200 mg/m(2) temozolomide (n = 37), and monitored for hematological toxicity over a 5-year period.

RESULTS

Short-term, self-limited hematological toxicity grade 3/4 comprised anemia in 1 patient (3.5%) in the 28 patient-cohort of patients treated with (177)Lu-octreotate and capecitabine. One of these patients (3.5%) later developed significant anemia and one developed thrombocytopenia (3.5%) over a median follow-up of 60 months (SD 20). The incidence of short-term grade 3/4 reversible myelosuppression in 37 patients after (177)Lu-octreotate/capecitabine/temozolomide was zero. Long- term follow-up for a median of 36 months (SD 11) showed significant thrombocytopenia in 2.7% and neutropenia in 2.7% of the patients and anemia in 10.8% of the patients (n = 4). The 3-year median hemoglobin and platelet and neutrophil counts trended downwards, but remained within normal ranges. Two patients in this cohort developed myelodysplastic syndrome.

CONCLUSION

The modest reversible hematological toxicity of PRRT of GEP NETs is not significantly increased by the addition of radiosensitizing chemotherapy with capecitabine and temozolomide in combination with (177)Lu-octreotate, which has the potential to enhance the efficacy of radiopeptide therapy.