Neuroendocrine tumors and diabetes mellitus: which treatment and which effect.

Diabetes mellitus (DM) and neuroendocrine tumors (NET) can exert unfavorable effects on each other prognosis. In this narrative review, we evaluated the effects of NET therapies on glycemic control and DM management and the effects of anti-diabetic therapies on NET outcome and management. For this purpose, we searched the PubMed, Science Direct, and Google Scholar databases for studies reporting the effects of NET therapy on DM as well as the effect of DM therapy on NET. The majority of NET treatments appear to impair glycaemic control, both inducing hypoglycemic or, more commonly, hyperglycemia and even new-onset DM. However, glucose metabolism imbalance can be effectively managed by modulating anti-diabetic therapy and adopting an appropriate nutritional approach. On the other hand, the effects of anti-diabetic treatment, like insulin, sulfonylureas, thiazolidinediones, ipeptidyl-peptidase-4 inhibitors, Glucagon-like peptide-1 receptor agonists, and Sodium-glucose cotransporter-2 inhibitors on NET are unclear. Recently, metformin has been investigated in patients with gastroenteropancreatic NET resulting in improved progression free survival suggesting a potential antineoplastic role. Finally, the management of DM in patients with NET is of great clinical relevance to correctly perform radiological procedures and even more functional imaging procedures, as well as to optimize the therapy and avoid treatment withdrawal or discontinuation. In conclusion, understanding the mechanisms underlying therapy-induced DM and implementing appropriate monitoring and management strategies of DM are essential for optimizing NET patient outcome and quality of life.