Cachexia in Cancer
Cachexia is wasting of both adipose tissue and skeletal muscle. It occurs in many conditions and is common with many cancers when their control fails. Some cancers, especially pancreatic and gastric cancers, cause profound cachexia. Affected patients may lose 10 to 20% of their body weight. Men tend to experience worse cachexia due to cancer than women do. Neither tumor size nor the extent of metastatic disease predicts the degree of cachexia. Cachexia is associated with reduced response to chemotherapy (see also Overview of Cancer Therapy), poor functional performance, and increased mortality.
The primary cause of cachexia is not anorexia or decreased caloric intake. Rather, this complex metabolic condition involves increased tissue catabolism; protein synthesis is decreased and degradation increased. Cachexia is mediated by certain cytokines, especially tumor necrosis factor-alpha, IL-1b, and IL-6, which are produced by tumor cells and host cells in the tissue mass. The ATP-ubiquitin-protease pathway plays a role as well.
Cachexia is easy to recognize, primarily by weight loss, which is most apparent with loss of temporalis muscle mass in the face (Hippocratic facies). The loss of subcutaneous fat increases the risk of pressure ulcers over bony prominences.
Treatment involves treatment of the cancer. If the cancer can be controlled or cured, cachexia resolves.
Additional caloric supplementation does not relieve cachexia. Any weight gain is usually minimal and is likely to consist of adipose tissue rather than muscle. Neither function nor prognosis is improved. Thus, in most patients with cancer and cachexia, high-calorie supplementation is not recommended. Parenteral nutritional support is not indicated except in situations where oral intake of adequate nutrition is impossible.
However, other treatments can mitigate cachexia and improve function. Corticosteroids increase appetite and may improve a sense of well-being but do little to increase body weight. Likewise, cannabinoids (marijuana, dronabinol) increase appetite but not weight. Progestogens, such as megestrol acetate, 40 mg po bid or tid, may increase both appetite and body weight. Drugs to alter cytokine production and effects are being studied.
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