RecruitingClinical trialEuropean Prospective Investigation Into Childhood CancerOver the last decades, research has shown that poor nutritional status can adversely impact prognosis and increase toxicities during treatment for childhood cancer. EPICkids is a collaboration between the International Initiative for Pediatrics and Nutrition, the International Agency for Research on Cancer, and sites throughout three Southern European countries (Spain, Greece, and Italy). The primary aim of EPICkids is to establish an informational resource on critical nutrition parameters wherein we can describe the trajectory of nutritional status among Southern European children and adolescents with acute lymphoblastic leukemia (ALL) and favorable biology brain tumors, investigate lifestyle behaviors, sociodemographic factors, and quality of life and correlate these indicators with clinical outcomes. The specimens obtained with the proposed study will foster future studies on nutrition and prevalent childhood cancer as well as establish a framework to develop evidence-based guidelines for European children with cancer, utilizing regional, European data. We plan to recruit 900 patients with ALL and 1400 patients with a favorable biology brain tumor over five years. Nutrition parameters and lifestyle factors will be measured at systematic timepoints over the study period. Stool and blood specimens will be collected at each timepoint. Eligible patients will be between 3 and 21 years of age.