Genetics of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (pNETs) represent a relatively rare disease; however, the incidence has been increasing during the last 2 decades. Next generation sequencing has greatly increased our understanding of driver mutations in pNETs. Sporadic pNETs have consistently presented with mutations in MEN1, DAXX/ATRX, and genes related to the mammalian target of rapamycin pathway. Inherited pNETs have traditionally been associated with multiple endocrine neoplasia type 1, von Hippel-Lindau syndrome, neurofibromatosis type 1, and tuberous sclerosis complex. The current review expands on the existing knowledge and the relevant updates on the genetics of pNETs.

A Direct Comparison of Patients With Hereditary and Sporadic Pancreatic Neuroendocrine Tumors: Evaluation of Clinical Course, Prognostic Factors and Genotype-Phenotype Correlations

Introduction

Pancreatic neuroendocrine tumors (PNETs) in hereditary syndromes pose a significant challenge to clinicians. The rarity of these syndromes and PNETs itself make it difficult to directly compare them with sporadic PNETs. Despite research suggesting differences between these two entities, the same approach is used in hereditary and sporadic PNETs.

Methods

We included 63 patients with hereditary PNET (GpNET) and 145 with sporadic PNET (SpNET) in a retrospective observational study. Clinical and genetic data were collected in two Polish endocrine departments from January 2004 to February 2020. Only patients with confirmed germline mutations were included in the GpNET cohort. We attempted to establish prognostic factors of metastases and overall survival in both groups and genotype-phenotype correlations in the GpNET group.

Results

Patients with GpNET were younger and diagnosed earlier, whereas their tumors were smaller and more frequently multifocal compared with patients with SpNET. Metastases occurred more frequently in the SpNET group, and their appearance was associated with tumor size in both groups. GpNET patients had longer overall survival (OS). OS was affected by age, age at diagnosis, sex, grade, stage, tumor diameter, occurrence and localization of metastases, type of treatment, and comorbidities. In the MEN1 group, carriers of frameshift with STOP codon, splice site, and missense mutations tended to have less advanced disease, while patients with mutations in exon 2 tended to have metastases more frequently.

Conclusions

Direct comparisons of GpNET and SpNET demonstrate significant differences in the clinical courses of both entities, which should force different approaches. A larger group of patients with GpNET should be assessed to confirm genotype-phenotype correlations.

Multiple Endocrine Neoplasia Type 1: Latest Insights

Multiple endocrine neoplasia type 1 (MEN1), a rare tumor syndrome that is inherited in an autosomal dominant pattern, is continuing to raise great interest for endocrinology, gastroenterology, surgery, radiology, genetics, and molecular biology specialists. There have been 2 major clinical practice guidance papers published in the past 2 decades, with the most recent published 8 years ago. Since then, several new insights on the basic biology and clinical features of MEN1 have appeared in the literature, and those data are discussed in this review. The genetic and molecular interactions of the MEN1-encoded protein menin with transcription factors and chromatin-modifying proteins in cell signaling pathways mediated by transforming growth factor β/bone morphogenetic protein, a few nuclear receptors, Wnt/β-catenin, and Hedgehog, and preclinical studies in mouse models have facilitated the understanding of the pathogenesis of MEN1-associated tumors and potential pharmacological interventions. The advancements in genetic diagnosis have offered a chance to recognize MEN1-related conditions in germline MEN1 mutation-negative patients. There is rapidly accumulating knowledge about clinical presentation in children, adolescents, and pregnancy that is translatable into the management of these very fragile patients. The discoveries about the genetic and molecular signatures of sporadic neuroendocrine tumors support the development of clinical trials with novel targeted therapies, along with advancements in diagnostic tools and surgical approaches. Finally, quality of life studies in patients affected by MEN1 and related conditions represent an effort necessary to develop a pharmacoeconomic interpretation of the problem. Because advances are being made both broadly and in focused areas, this timely review presents and discusses those studies collectively.

The efficacy of everolimus and sunitinib in patients with sporadic or germline mutated metastatic pancreatic neuroendocrine tumors

Background

Hyperactivation of mTOR pathway and angiogenesis have been implicated in the pathogenesis of neuroendocrine tumors (NETs). Everolimus, an oral inhibitor of mTOR, and sunitinib, an antiangiogenic drug, are effective targeted therapies approved to treat locally advanced/metastatic pancreatic neuroendocrine tumors (pNETs). Most pNETs are sporadic and mutations in genes involved directly or indirectly in mTOR pathway regulation have been implicated, including somatic mutation in MEN1 in 44% of cases. About 10% of pNETs can be part of hereditary syndromes, e.g., multiple endocrine neoplasia type 1 (MEN1) and Von-Hippel Lindau (VHL), and these patients are underrepresented in pivotal phase III trials. We hypothesized that everolimus would be particularly effective in patients with MEN1-associated pNETs. Likewise, we inferred that sunitinib would also be beneficial to patients with VHL-associated pNETs.

Methods

We conducted a multicenter retrospective and comparative study to assess the efficacy of everolimus and/or sunitinib in a cohort of patients with advanced pNETs with or without known MEN1 or VHL syndrome. The evaluation of the germline mutational status of VHL and MEN1 genes was retrospectively collected from the medical records. The primary endpoints were progression free survival (PFS) and time to treatment failure (TTF) of patients who received at least one month of sunitinib or everolimus in monotherapy.

Results

Thirty-three patients were identified from September 2009 to April 2018. Most were male 60.6%. Median Ki67 was 9%, liver metastases were present in 97%. The majority of tumors were non-functioning. Thirty-one patients received everolimus, of them 8 patients had germline mutations (6 in MEN1 and 2 in VHL genes). Nine patients received sunitinib, of them 3 had germline mutation (2 in MEN1 and 1 in VHL genes). In a median follow up of 26 months, among everolimus-treated patients, mTTF and mPFS were numerically superior in patients with germline mutations compared with those with sporadic pNETs (mTTF: 16.1 vs. 9.9 months, P=0.888; mPFS: 33.1 vs. 12.3 months, P=0.383). The disease control rate with everolimus was numerically higher in favor of germline mutated tumors compared to sporadic ones (87.5% vs. 68.4%). Sunitinib was used by 1 patient with VHL syndrome, achieving a PFS of 17.6 months. In the subgroup of sporadic pNETs, sunitinib was used by 6 patients reaching a mPFS of 18 months (range, 5-25 months), predominantly in second line.

Conclusions

Our study suggests that everolimus may offer a prolonged tumor control in pNETS with germline mutations (MEN1 or VHL) compared to sporadic ones. The small number of patients and the retrospective nature of this study precludes any definitive conclusions.

Molecular Diagnostics in the Neoplasms of the Pancreas, Liver, Gallbladder, and Extrahepatic Biliary Tract: 2018 Update

Pancreatic neoplasms, including ductal adenocarcinoma, solid pseudopapillary neoplasm, pancreatic endocrine neoplasms, acinar cell carcinoma, and pancreatoblastoma, are associated with different genetic abnormalities. Hepatic adenomas with beta-catenin exon 3 mutation are associated with a high risk of malignancy. Hepatic adenoma with arginosuccinate synthetase 1 expression or sonic hedgehog mutations are associated with a risk of bleeding. Hepatocellular carcinoma and choangiocarcinoma display heterogeneity at both morphologic and molecular levels Cholangiocellular carcinoma is most commonly associated with IDH 1/2 mutations.

Guidelines for the management of neuroendocrine tumours by the Brazilian gastrointestinal tumour group

Neuroendocrine tumours are a heterogeneous group of diseases with a significant variety of diagnostic tests and treatment modalities. Guidelines were developed by North American and European groups to recommend their best management. However, local particularities and relativisms found worldwide led us to create Brazilian guidelines. Our consensus considered the best feasible strategies in an environment involving more limited resources. We believe that our recommendations may be extended to other countries with similar economic standards.