Appetite for change - The need to revisit malnutrition screening and assessment in oncology

Malnutrition is highly prevalent among oncology patients, with large-scale studies reporting involuntary weight loss in 31-87%, depending on tumour site and disease stage. Driven by a combination of nutrition-impact symptoms, reduced oral intake, and systemic inflammation, leading to poor treatment tolerance, diminished quality of life, and reduced survival. Systemic inflammation is a hallmark of cancer-associated malnutrition and contributes to loss of lean mass and abnormal body composition phenotypes such as sarcopenia, cachexia, and myosteatosis, which may coexist with overweight or obesity. Malnutrition screening tools are widely used to identify patients at risk; however, traditional weight and BMI-based instruments such as the Malnutrition Screening Tool (MST) and Malnutrition Universal Screening Tool (MUST) frequently misclassify patients with cancer as well-nourished. These tools fail to account for nutrition-impact symptoms, inflammation, and muscle wasting. Although obesity is an established cancer risk factor, 40-60% of patients remain overweight or obese during treatment, even those with metastatic disease. When screening tools are BMI-based, high fat stores mask muscle wasting, leading to misclassification of nutritional risk and delayed dietetic referrals. To improve detection, screening tools should incorporate patient-reported symptoms, inflammatory markers, and body composition assessment, enabling earlier, proactive nutritional care. Alternatively, it may be time to acknowledge that all cancer patients are inherently "at risk" of malnutrition and to prioritise universal access to dietetic support from diagnosis through treatment. This review summarises current malnutrition screening and assessment practices in oncology and outlines key considerations for future research and clinical practice.