The mechanisms of the development of cancer cachexia are complex and not completely under- stood. Costa (1977) likened the cachectic state to the diseases of protein-calorie malnutrition, kwashiorkor, and marasmus, which are more commonly seen in relatively undeveloped areas of the world. In fact, patients with advanced cancer may lose significant amounts of nitrogen and fat and exhibit protein-calorie malnutrition (Nixon et al., 1980). As with malnutrition, some of the characteristics of cachexia may be overcome by forced feeding programs involving either total parenteral nutrition, that is, intravenous feeding, or hyperalimentation by means of stomach intubation or similar methods. However, such methods do not appear to prolong survival or af- fect many of the complications of advanced neoplasia (Balducci and Hardy, 1985; Vigano et al.,1994). In view of this lack of effectiveness of such nutritional modalities, various pharmacologi- cal approaches to the treatment of cachexia in advanced cancer patients have been utilized (Loprinzi et al., 1992; Vigano et al., 1994). The drug therapy utilized involves either hormones
Table 17.1 Manifestations of Cancer Cachexia
2. Weight loss
3. Asthenia (weakness)
4. Changing body image
5. Chronic nausea
6. Negative energy balance
7. Anemia, metabolic alterations (protein, lipid, carbohydrate)
such as corticosteroids, progestational drugs, and anabolic steroids administered in an attempt to change the altered hormonal milieu of the tumor-bearing host or mood-altering drugs such as cannabinoids to alter the psychology of the host. In the final analysis, however, cancer cachexia cannot be completely reversed without the elimination of the neoplasm (van Eys, 1982).
Warnold and associates (1978) demonstrated that the development of cachexia may be ac- companied by an increase in the resting metabolic rate and the daily energy expenditure in can- cer patients, even in the absence of significant physical activity. In comparing cancer patients with healthy subjects, these authors found that while energy intake was not significantly differ- ent between the two groups, the daily energy expenditure and resting metabolic rate were signif- icantly greater in cancer patients than in controls (Table 17.2). Shortly thereafter, Bozzetti and colleagues (1980) reported that resting metabolic rates were increased by 60% in a heteroge- neous group of 65 patients with advanced cancer. These investigators found a significant correla- tion between resting metabolic expenditure and percentage of body weight loss. Furthermore, a number of investigations have found that weight loss in cancer patients, especially that found at initial diagnosis, had a dramatic effect on survival (Table 17.3). This table shows that weight loss is quite common in patients with cancer, and it may be stated that nearly every patient who dies from cancer will develop weight loss at some time during the course of the disease (Langstein and Norton, 1991).