Malnutrition in cancer patients: Causes, consequences and treatment options.

Cancer patients are at a high risk of malnutrition and disease-associated catabolic derangements. It is important to differentiate between 'simple' - voluntary or involuntary - caloric restriction with protein-sparing ketogenic metabolic adaptation and cachexia, characterized by the combination of weight loss and dysmetabolism, most prominently systemic inflammation. While both conditions result in the sacrifice of fat and protein stores and thus impact on treatment tolerance, complication rates and survival, the presence of metabolic derangements is especially dangerous by straining multiple organ functions. To avoid underdiagnosing and undertreating malnutrition, all cancer patients should be routinely screened for nutritional risk. At-risk patients require comprehensive assessment for contributing and treatable causes and, if available, multi-professional efforts to improve food intake, support anabolism, alleviate distress and antagonize pro-inflammatory processes. In curative settings, anabolic support should accompany or even precede anticancer treatments. Prehabilitation before major surgery, has been studied extensively, including muscle training as well as nutritional and/or psychological support. Recent meta-analyses report a consistent benefit on functional capacity and possible improvement in postoperative complications and length of hospital stay. In palliative settings, prevailing catabolic derangements require careful assessment of the individual constellation of disturbed functions and an empathic evaluation of benefits and risks of nutritional interventions. This is of special relevance in patients with an expected survival of less than a few months. Due to the complex interactions of mechanical, metabolic and psychological factors, multi-professional teams should be involved.