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.