GALENOS 1 is a prospective observational study designed to explore longitudinal changes in nutritional status and body composition in patients with head and neck squamous cell carcinoma, locally advanced rectal cancer, and lung cancer undergoing standard antineoplastic treatments. The study is the preparatory observational component of the FOR-GALE PREVENTION project, which aims to support the future development of a galenic immunonutrition dietary supplement intended to reduce adverse events and improve treatment compliance