BackgroundLow muscle mass and malnutrition are independently associated with an increased risk of adverse outcomes in patients with cancer. However, it is not yet clear which parameter is most indicative of these risks. This study investigates the prognostic significance of different parameters reflecting malnutrition and muscle health in a well-characterised oncology population at nutritional risk. MethodsThis preplanned secondary analysis included patients with cancer from a Swiss-wide, randomised-controlled nutritional trial. We investigated associations among malnutrition markers (i.e., malnutrition diagnosis based on modified Global Leadership Initiative on Malnutrition (GLIM) criteria, albumin concentration) and muscle health markers (i.e., hand grip strength, computed tomography (CT)-based muscle mass and radiodensity) with 180-day all-cause mortality (primary outcome). ResultsWe included 269 patients with a main admission diagnosis of cancer and available CT scans. In a mutually adjusted model, four parameters contributed to risk assessment including modified malnutrition diagnosis (GLIM) (HR 1.78 (95%CI 1.17 to 2.69), p = 0.007, AUC 0.58), low albumin concentration (HR 1.58 (95%CI 1.08 to 2.31), p = 0.019, AUC 0.62), low handgrip strength (HR 2.05 (95%CI 1.43 to 2.93), p = 0.001, AUC 0.62) and low muscle radiodensity (HR 1.39 (95%CI 0.90 to 2.16), p = 0.139, AUC 0.63). Combining these parameters resulted in a model with high prognostic power regarding 180-day mortality (overall AUC 0.71). ConclusionsIn this study of inpatients with cancer at nutritional risk, several malnutrition and muscle health parameters emerged as independent prognostic indicators for mortality. The use of these parameters may improve risk stratification and guide nutritional interventions in this vulnerable population. Trial registrationClinicalTrials.gov, number NCT02517476.