CANCER CACHEXIA

Cachexia is a common problem in the clinical management of cancer patients, particularly those with solid tumors. Cachexia is most obviously manifested as weight loss with massive depletion of both adipose tissue and muscle mass, and death is probably due to loss of lean body tissue. Not only is the survival time shorter in patients with cachexia, but the frequency of response to chemotherapy is also significantly reduced. Although anorexia frequently accompanies cachexia, attempts to halt or reverse cachexia by nutritional repletion have not been successful. This suggests that cachexia is due to metabolic abnormalities produced by the tumor in addition to the underlying anorexia. In some patients weight loss is associated with an increased relative energy expenditure possibly through an elevated adrenergic state. Several factors have been postulated as mediators of cancer cachexia and can be divided into two groups. (i) Materials with hormone-like characteristics which result in direct catabolism of host tissues. (ii) Cytokines which cause alterations in host metabolism indirectly. Included in group (i) are the conventional catabolic hormones and a lipid mobilizing factor (LMF) produced by tumors, which causes direct breakdown of adipose tissue. Included in group (ii) are tumor necrosis factor-alpha, interleukin-6, interferon-gamma and leukaemia inhibitory factor. The materials appear to influence adipose tissue indirectly through an inhibition of lipoprotein lipase. Reversal of cachexia has been achieved by two groups of agents. (i) Those stimulating food intake, e.g. megestrol acetate. (ii) Those directly inhibiting the LMF, e.g. eicosapentaenoic acid. While agents in group (i) can cause tumor growth stimulation, those in group (ii) act as tumor growth inhibitors. This latter results suggests that the products of catabolism of host tissues may be important for tumor growth and provides a new avenue for chemotherapeutic intervention.