|Protein-Energy Interactions (International Dietary Energy Consultative Group - IDECG, 1991, 437 pages)|
|Effects of disease on desirable protein/energy ratios|
|5. Possible role of specific amino acids|
Malnutrition occurs commonly as a consequence of cancer and represents an important prognostic sign. Response to treatment and survival are inversely correlated to the degree of weight loss, although intestinal obstruction may contribute to weight loss in some cancers. In most instances, the development of malnutrition in cancer is a systemic response to the tumor and is principally due to anorexia and reduced intake rather than through changes in energy expenditure. Therefore, protein and energy are more equally depleted than with infection. However, similar to infection (STREAT et al., 1987), nutritional repletion is ineffective in cancer cachexia that develops as a systemic reponse (NIXON et al., 1981).
The usual chemotherapy regimen for most tumors is of short duration, and although anorexia and weight loss commonly occur, chemotherapy does not elicit a severe catabolic response. Thus, it is not surprising that data from a number of randomized clinical trials investigating the role of invasive nutritional support during chemotherapy did not identify a net benefit (KLEIN et al., 1986).
In bone marrow transplantation, however, the chemotherapy regimens are much more aggressive and prolonged, and malnutrition resulting from these regimens can be clinically important. Nutritional support under these circumstances has been shown to benefit morbidity, mortality and treatment outcome (WEISDORF et al., 1987). A corollary finding in many of the randomized clinical trials was that infectious morbidity was greater in the fed group due to poor management. Excess carbohydrate calories that produce significant hypoglycemia or excess parenteral fat administered too rapidly have been shown to diminish immune function. These findings emphasize that nutritional support therapies must be provided in an expert manner with attention to an appropriate P/E ratio. This becomes critical with parenteral alimentation. Nutritional support has the potential to cause complications and worsen outcomes if not done well.
Radiation therapy is usually longer than chemotherapy and can lead to significant anorexia. Nutritional support to the malnourished may be more likely to improve outcome when intense radiotherapy courses are provided that include the abdomen in the radiated field. However, there are insufficient data to recommend routine adjuvant nutritional support during radiotherapy.
With gastrointestinal cancer, where local obstructive symptoms may commonly be a cause of malnutrition (i.e., cancer of the esophagus), nutritional support can replete lean tissue and will improve nutritional status prior to the planned stress of major surgery as well as improve outcome (MULLER et al., 1982).
When malnutrition develops from the metabolic response to injury or inflammation as seen in trauma, infection, inflammatory disease, and cancer, nutritional therapy adequate in terms of protein and energy may reduce the rate of tissue loss. However, it will not replete lean tissue during the acute phase, although fat gain can be achieved (STREAT et al., 1987; NIXON et al., 1981).