Malnutrition and Sarcopenia in Patients with Neuroendocrine Tumors: A Comprehensive Review of Evidence

Neuroendocrine neoplasms (NENs) are rare and heterogeneous tumors with heterogeneity in morphology and molecular profile and consequently resulting in a heterogeneous biological behavior. They have a more indolent natural history compared to the classic cancer and may emerge in any site of the human body, but usually they have gastroenteropancreatic (GEP) or bronchopulmonary (BP) origin. When NENs are well differentiated, they are called neuroendocrine tumors (NETs) as opposed to poorly differentiated neuroendocrine carcinomas (NECs). They may secrete a bioactive molecule resulting in a secretory syndrome or they may not be associated with any secretory product, defining functional and non-functional NENs. The hormonal hypersecretion syndromes, the chronic symptom burden, the tumor-related inflammation, and the treatment side effects impair nutritional intake and absorption while increasing metabolic needs. The present comprehensive narrative review is summarizing established and emerging methods of nutritional and body composition assessment, and the recent evidence of interventions for sarcopenia and malnutrition in patients with NETs. Early identification and management of malnutrition and sarcopenia are fundamental steps to improve quality of life and clinical outcomes in these patients during the long natural history of these neoplasms.