The influence of radiotherapy on the protein intake and muscle mass of patients has not been extensively investigated to date. It is also unclear whether the localization of the tumor disease and thus the radiation field have different effects. Therefore, with the pilot study presented here, we would like to record the nutritional uptake of patients before and after radiotherapy. The aim is to determine the amount of energy and protein intake as well as the timing of protein intake. Furthermore, the relationship between the timing of protein intake and muscle mass will be investigated.

Many studies have shown that cancer patients have a very high prevalence of malnutrition. Several large-scale studies have reported that 50-80% of these patients are affected by involuntary weight loss, with the extent of weight loss depending on the tumor location and the type and stage of the disease. It has been widely reported that nutritional interventions are essential in cancer patients. Nevertheless, nutritional support is still not universally accessible to all patients. Given the prevalence of nutritional risks, the treatment of lean muscle mass loss remains a challenge in clinical practice. For this reason, a multidisciplinary approach with targeted nutritional therapy is crucial to improve the quality of care in oncology. A protein level of 1-1.2 g/kg bw is suggested for the maintenance of muscle mass.However, it has been shown that this amount is not sufficient to support ALM in patients with tumor diseases. Only an amount above 1.4 g/kg bw has been associated with a positive effect on muscle mass. Adequate dietary protein intake is essential for the maintenance of numerous physiological processes, including muscle protein synthesis and muscle function. Sufficient energy and protein intake is necessary to support muscle protein synthesis. The scientific literature frequently discusses the relationship between daily protein intake and its distribution over the main meals. The evening meal is particularly important for the maintenance of ALM.

Inclusion Criteria:

• Capacity to consent
• At least 45 years of age
• Sufficient knowledge of the German language
• Indication to undergo radio(chemo)therapy with at least 10 fractions

Exclusion Criteria:

• Participation in other interventional studies
• Pregnancy/breastfeeding
• Previous intake of high-calorie supplementary food or intravenous nutrition
• BMI < 18.5
• When performing the bioimpedance measurement: patients with pacemakers, defibrillators and other implanted automatic devices

Indication for radio(chemo)therapy in the presence of one of the following histologically confirmed tumor diseases: Thorax, head and neck, breast, abdomen/pelvis, brain, bone metastases, prostate