Résumé
Up to 50% of patients with cancer suffer from weight loss and undernutrition (as called cachexia) even though it is rarely screened or properly handled. Patients' prognosis and quality of life could be greatly improved by simple and inexpensive means encompassing nutritional status assessment and effective nutritional care. These guidelines aim to give health professionals and patients practical and up-to-date advice to manage nutrition in the principal situations encountered during the cancer course according to the type of tumour and treatment (i.e. radio and/or chemotherapy). Specific suggestions are made for palliative and elderly patients because of specific risks of undernutrition and related comorbidities in this subset. Levels of evidence and grades of recommendations are detailed as stated by current literature and consensus opinion of clinical experts in each field.