The aetiology and management of weight loss and malnutrition in cancer patients.

Abnormal values of parameters generally associated with description of protein or energy stores are often observed in cancer patients. The aetiology of these abnormal values is not clear, but seems to include insufficient energy intake absolutely (anorexia), or relative to energy needs (increased energy expenditure). In addition, the ability of some tissues to acquire nitrogen and energy seems to be changed when cancer is present. The resulting status described by abnormal values of protein or energy store parameters is often incorrectly referred to as malnutrition. Incorrect because many factors other than nutrition are related to the development of this condition. However, the presence of the so-called malnutrition is associated with increased morbidity, decreased survival and decreased tolerance to cancer therapy. Whether nutritional therapy is able to reverse these adverse effects by malnutrition remains unproven: most trials performed in an attempt to prove such restoration of the individual's ability to withstand cancer and its treatment, display such conceptual flaws that a convincing answer cannot be given. On the other hand, a deleterious effect of nutritional support has not been observed. More, and clinically relevant, research needs to be performed in this field.