Physical function in men and women with cancer. Effects of anemia and conditioning.
Fatigue is an extraordinarily common consequence of cancer and its treatment. Fatigue can result in diminished cognitive and physical functional capacity and may be the result of multiple causes. However, aside from psychological factors, the main physiological factors leading to fatigue in cancer patients are anemia, severe deconditioning, and muscle wasting that is secondary to cachexia. One of the most common measures of functional capacity is maximal aerobic capacity, also called VO2max. VO2max is a measurement of the maximal capacity of the entire cardiorespiratory system and muscles to consume oxygen. It is strongly predictive of functional status, and it is strongly related to circulating hemoglobin. Research has indicated that the use of recombinant human erythropoietin to treat anemia can preserve or increase VO2max. In addition, aerobic exercise training has been demonstrated to greatly relieve symptoms of fatigue in patients with cancer. It is both safe and effective in this patient population. Muscle wasting results in diminished protein reserve and extreme muscle weakness. Progressive resistance exercise training has been demonstrated to greatly increase strength, improve protein balance, and increase muscle mass even in very frail and old men and women. It should be strongly encouraged in patients experiencing muscle wasting and weakness. A comprehensive "cancer rehabilitation"program is described, which is made up of (1) correcting anemia related to cancer or its treatment; (2) aerobic conditioning to improve VO2max; and (3) progressive resistance exercise in patients experiencing muscle weakness or wasting. In this way, the physiological causes of fatigue may be addressed and quality of life improved.
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