Gastroenteropancreatic Neuroendocrine Neoplasms Grade 3 : Biological and Clinical Aspects

Abstract: The aim of this thesis was to investigate biological and clinical aspects of G3 gastroenteropancreatic neuroendocrine neoplasms (G3 GEP-NENs).In our first study, the expression of the tumor suppressor p53 was investigated. In a cohort of G3 GEP-NENs we found the expression of p53 protein to be present in 39% of 124 cases. Expression of p53 correlated to poorer progression-free survival (PFS) and overall survival (OS) for patients with G3 GEP-NENs originating from colon or rectum. In the next study, we aimed to demonstrate the prevalence of PD-L1 expression in G3 GEP-NENs and its possible clinical importance. Ten per cent of 136 tumor specimens were immunoreactive for PD-L1 in either tumor cells or immune cells. In contrast to p53 expression that could be correlated to PFS and OS in a subgroup of patients the expression of PD-L1 did not correlate to any clinicopathological variables and conclusively, PD-L1 may not have a vital role for the pathogenesis of G3 GEP-NENs. In a further study, we sought to identify new potential biomarkers and a panel of immuno-oncological proteins were measured in serum collected from pancreatic G3 NENs and healthy controls. Out of 87 proteins, 62% were significantly lower in serum concentration in healthy controls compared to patients. One protein, FasL, was present in significantly higher levels in healthy controls compared to patients. FasL may have a protective role in its ability to activate T cells in the immune system. Other proteins of interest were chemokine (c-c motif) ligand and interleukin 8 that both correlated to poorer prognosis in G3 pancreatic NEN patients. More studies are needed for further understanding of the roles and clinical relevance of immuno-oncological proteins in G3 pancreatic NENs.Finally, we evaluated whether intravenous or oral administration of etoposide differed with regards to PFS and OS in patients with G3 GEP-NENs. There was no significant difference in PFS nor OS between patients receiving oral compared to intravenous etoposide; demonstrating that an oral option of etoposide is not inferior in its efficacy as compared to the more used intravenous formulation. These results suggest that considering oral options of etoposide is important since they are more often preferred by patients, increase the quality of life for the patients and reduce hospital costs.This thesis has contributed to an understanding of the distribution and clinical relevance of p53 and PD-L1 in GEP-NENs. A potential role of FasL, chemokine and interleukin 8 as prognostic and/or diagnostic factors in pancreatic G3 NENs has been identified and should be further investigated. The thesis also gave some insight into the role of oral etoposide as an alternative option to intravenous formulation with regards to efficacy. Oral formulations are preferred by many patients and improve quality of life while decreasing hospital-related costs. Further studies are needed to compare the tolerability of oral formulation compared to the intravenous formulation.