Influence of Tumour and Patient's Related Factors on the Response to Medical Treatments in Well Differentiated GEP-NENs

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) represent the most common NeuroEndocrin Neoplasms (NEN) site, comprising 55-70% of all NENs, and they are extremely heterogeneous diseases in terms of clinical presentation and aggressiveness. In recent years there has been a significant increase in the incidence of such neoplasms, partially due to incidental findings of small indolent lesions. However, the behavior of GEP- NEN is variable and mainly dictated by some factors as age, sex, histologic grade, primary site, and stage at diagnosis1. As for grade which is defined by the proliferative activity as measured by mitotic count or ki67 staining, some 75% of neoplasms fall into the G1 grading category, 15% into the G2 category, and 10% into the G3 category. The probability of developing metastases is directly correlated with grading. In addition, the grading of GEP-NENs is also correlated with the type of differentiation of the neoplasm (well differentiated or poorly differentiated). Managing the complexity of this type of neoplasm has made it necessary to stratify patients into progression risk classes. The therapeutic approach is accordingly defined, and may include different treatments (surgery, loco-regional, targeted therapies, chemotherapies,...). Among treatments, the most widely used for patients with well-differentiated NENs are somatostatin analogs (SSAs), targeted therapies, and the combination of oral capecitabine and temozolomide. Systemic intravenous chemotherapy is instead employed in a subset of G3 neoplasms, especially if poorly differentiated.