Cancer and various antitumor treatments can have adverse effects on the nutritional status of the affected patient. It is important have an understanding of these effects in order to provide nutritional support. As a tumor grows it produces both local and distant effects. The distant effects are known as paraneoplastic syndromes. These include –
Anorexia or loss of appetite occurs due to the presence of an malignant tumour Anorexia is intensified by fear, depression, sepsis and treatment. When severe it can lead to protein calorie malnutrition and wasting of body tissues – commonly known as cachexia. The anorexia and weight loss produced in cancer depends on the type of tumour. The maximum loss is seen in gastric cancers and pancreatic cancers (> 80%) while colon, prostrate and lung cancers also lead to considerable weight loss (48-61%). Breast cancers cause a weight loss of 30 – 40%. In general there is an average loss of 63% weight in general cancer populations.
Some tumours produce insulin like substances and use up glucose leading to hypoglycemia. Serious weight loss and nutrient deficiencies have effect on metabolic and immune function with resulting morbidity and mortality. Tube feeding helps in maintaining host weight but it is important to follow it with anti-tumour therapy. Otherwise it may lead to undesirable metabolic reactions.
Increased rate of Cori cycling is seen in cancer patients. In this cycle glucose is metabolized to lactate which is resynthesized to glucose. This cycle uses up 6 ATP molecules. However only two ATPs are produced by glycolysis through which the glucose molecules pass. Thus this is a ‘futile cycle’ in which more energy is used up than produced and is important for development of weight loss.
Tumors also mobilize fat stores for their own use. This not only depletes fat stores but also increases plasma lipid levels which can be immunosuppressive.
Excess body fat depletion, increased lipolysis, increase in free fatty acid level, decreased lipogenesis and decrease in activity of serum lipoprotein lipase are all attributed to stress response to illness leading to an increase in catecholemines.
Increased whole body protein turnover is seen. Persistent muscle proteins break down and a decrease in plasma branched chain amino acids is seen. Albumin synthesis is depressed due to malnutrition and there is an increased degradation by tumour liposomes both leading to hypo albuminemia.
Taste and appetite changes. Unpleasant and unacceptable alterations in the taste of foods occur. The taste threshold for sweetness is elevated while that for bitterness is lowered.
Hypercalcemia is a common metabolic complication as the tumour releases substances which cause bone resorption. This leads to nausea, muscle weakness, excess urine, increase in blood pressure and anorexia.
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