Defining Tumor Microenvironment as a Possible Target for Effective GEP-NENs Immunotherapy-A Systematic Review

Neuroendocrine neoplasms (NENs) are a heterogenous and recurrent group of malignancies originating from neuroendocrine secretory cells diffused on all parts of the human body. Gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs) account for most NENs. Considering the abundance of possible origins, locations, and tumor specifications, there is still no consensus about optimal treatment options for these neoplasms. In light of the escalating immunotherapeutic approaches, it is crucial to define indications for such therapy in GEP-NETs. Bearing in mind the significance of pathophysiological mechanisms and tumor microenvironment (TME) impact on carcinogenesis, defining TME structure and correlation with the immune system in GEP-NETs appears essential. This paper aimed to assess the characterization of the tumor immune microenvironment for a better understanding of the possible therapeutic options in GEP-NETS. The authors performed a systematic review, extracting papers from the PubMed, Web of Science, and Scopus databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Among 3800 articles identified through database searching, 292 were assessed for eligibility. Ultimately, 28 articles were included in the qualitative synthesis. This paper sums up the research on the immune cell infiltrates, immune checkpoint expression, cytokine profile, neoangiogenesis, and microbiome in the TME of GEP-NETs.

Immunotherapy for gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs): a 2021 update

Neuroendocrine neoplasms (NENs) are a group of heterogeneous malignancies, arising from the neuroendocrine system. These neoplasms are divided into two distinct groups, the low-proliferating, well-differentiated neuroendocrine tumors (NETs), and the highly-proliferating, poorly-differentiated neuroendocrine carcinomas (NECs). Recent data demonstrate that the incidence of gastroenteropancreatic (GEP) neuroendocrine neoplasms, GEP-NETs and GEP-NECs, has increased exponentially over the last three decades. Although surgical resection is considered the best treatment modality, patients with GEP-NETs often present with advanced disease at diagnosis associated with a 5-year survival rate of 57% for well-differentiated tumors, and only 5.2% for small-cell tumors. Immunotherapy is a novel treatment approach, which has demonstrated effective and promising therapeutic results against several types of cancers. In the present study, we review the current ongoing clinical trials and to evaluate the efficacy of immunotherapy in GEP-NENs. Furthermore, we analyze the importance of tumor genetic profiling and its clinical implications in immunotherapy response.

Outcomes of small-cell versus large-cell gastroenteropancreatic neuroendocrine carcinomas: A population-based study

The recent World Health Organization classification for gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) classified poorly differentiated GEP-NENs into small cell and large cell categories. The present study aimed to assess the differences in outcomes between patients with both histological categories. The Surveillance, Epidemiology and End Results (SEER) database (1975-2016) was accessed and patients with small cell and large cell GEP-neuroendocrine carcinomas (NECs) were extracted. Differences in survival outcomes were explored through Kaplan-Meier survival estimates and multivariable Cox regression models. In total, 2204 patients with GEP-NEC were identified in the survival cohort, including 1698 patients with small cell NEC (77%) and 506 patients with large cell NEC (23%). Using Kaplan-Meier analysis/log-rank testing, large cell GEP-NEC was associated with better overall survival compared to small cell NEC (P < 0.01). Using multivariable Cox regression analysis, large cell GEP-NEC was associated with better overall survival (large cell GEP-NEC versus small cell GEP-NEC, hazard ratio = 0.77; 95% confidence interval = 0.68-0.86) and cancer-specific survival (large cell GEP-NEC versus small cell GEP-NEC, hazard ratio = 0.79; 95% 95% confidence interval = 0.69-0.91). Patients with small cell GEP-NEC have worse survival outcomes compared to those with large cell GEP-NEC. Further efforts are needed to identify biological differences and treatment sensitivities between both histological categories.