This multicenter, prospective cohort study investigates the long-term impact of nutritional status on clinical outcomes in cancer patients undergoing treatment in Shaanxi Province, China. It evaluates how malnutrition, dietary patterns, and nutritional interventions affect treatment tolerance, quality of life, and survival. The study tracks dynamic changes in nutritional health and related indicators throughout various stages of chemoradiotherapy, aiming to inform evidence-based strategies for precision nutrition in oncology care.