Nutritional status and weight trajectories during radiotherapy in patients with cancer: a retrospective cohort study

Patients receiving radiotherapy are frequently malnourished, and weight loss can negatively impact treatment tolerance and clinical outcomes.

This retrospective cohort study aimed to assess nutritional status, weight trajectories, and changes in the prognostic nutritional index (PNI) over time, during radiotherapy.

The medical records of 680 adult patients who initiated radiotherapy were reviewed retrospectively at a tertiary oncology center from 2023 to 2025. Patients were retained in the cohort regardless of subsequent treatment completion, provided they met predefined baseline eligibility criteria. Body weight, serum albumin and PNI were measured serially before, during and after radiotherapy. Weight and trajectory patterns of the PNI were described, toxicities associated with the treatment and nutritional interventions were evaluated, and multi-variable logistic regression models were constructed to identify factors associated with clinically marked weight loss (decrease of ≥5%).

Mean body weight decreased from 69.4 ± 14.8 kg at baseline to 65.8 ± 14.6 kg at treatment completion (p < 0.001). Clinically significant weight loss occurred in 44.6% of patients, while low PNI increased from 36.9 to 60.7%. Severe treatment-related toxicity, treatment interruption, hospitalization, and radiotherapy non-completion were significantly associated with weight loss and declining PNI trajectories (all p < 0.001). Nutritional support was associated with lower odds of weight loss (adjusted OR = 0.66, 95% CI: 0.46-0.94), although this finding should be interpreted cautiously because intervention timing was not consistently documented and causality cannot be established.

During radiotherapy, nutritional deterioration is common and is closely linked to poor treatment outcomes. Early nutritional assessment and intervention can reduce weight loss and improve tolerance to therapy in high-risk patients.