Progressive Deterioration in Dietary Intake and Nutritional Risk During Oncological Treatment in Children with Solid Tumors: A Prospective Longitudinal Study

Purpose Children with solid tumors are highly vulnerable to treatment-related nutritional compromise. However, longitudinal data describing how dietary intake and nutritional risk evolve during therapy remain limited. This study aimed to examine longitudinal changes in dietary intake adequacy and nutritional risk across different phases of oncological treatment and to identify clinically vulnerable periods requiring intensified supportive care. Methods In this prospective longitudinal study, children aged 8–18 years with newly diagnosed solid tumors were assessed at three predefined treatment phases (early, mid- and late-treatment). Dietary intake was evaluated using 3-day food records at each time point. Energy and nutrient intakes were expressed as percentages of age- and sex-specific estimated requirements. Nutritional risk was assessed using the Screening Tool for Childhood Cancer Nutrition Risk (SCAN). Longitudinal changes were analyzed using non-parametric repeated-measures methods, and associations with gastrointestinal symptoms and taste alterations were explored. Results Sixty children completed all assessments. Energy adequacy declined significantly over time (p = 0.001), with most patients failing to meet recommended energy requirements throughout treatment. Significant reductions were observed in carbohydrate, fat, dietary fiber, and selected micronutrients, particularly iron and magnesium. More than 80% of patients were classified as being at nutritional risk at all time points. Higher nutritional risk scores were significantly associated with greater gastrointestinal symptom burden and taste alterations (all p < 0.05). The mid-treatment phase emerged as the period of greatest nutritional vulnerability. Conclusions Children with solid tumors experience progressive deterioration in dietary intake adequacy during oncological treatment, with mid-treatment representing a critical window for intensified nutritional monitoring and supportive intervention. Integrating repeated dietary assessment with structured nutritional risk screening may enhance early identification of vulnerable patients and improve supportive care delivery in pediatric oncology.