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Cancer Health Center

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Fatigue (PDQ®): Supportive care - Health Professional Information [NCI] - Contributing Factors


A retrospective review was conducted to understand the problem of anemia in patients undergoing radiation therapy. Anemia was prevalent in 48% of the patients initially, and increased to 57% of the patients during therapy. It was more common in women than men (64% vs. 51%); however, men with prostate cancer experienced the greatest increase in anemia during radiation therapy.[32] In certain cancers, such as cancer of the cervix and cancer of the head and neck, anemia has been found to be a predictor of poor survival and diminished quality of life in patients undergoing radiation therapy.[33,34,35,36]

Nutrition Factors

Fatigue often occurs when the energy requirements of the body exceed the supply of energy sources.[37,38] In people with cancer, three major mechanisms may be involved:

  • Alteration in the body's ability to process nutrients efficiently.
  • Increase in the body's energy requirements.
  • Decrease in intake of energy sources.

Causes of nutritional alterations are listed in Table 1.

Table 1. Nutrition/Energy Factors

Altered ability to process nutrientsImpaired glucose, lipid, and protein metabolism
Increased energy requirementsTumor consumption of and competition for nutrients
Hypermetabolic state due to tumor growth
Decreased intake of energy sourcesAnorexia
Bowel obstruction

Psychologic Factors

Numerous factors related to the moods, beliefs, attitudes, and reactions to stressors of people with cancer can also contribute to the development of chronic fatigue. Anxiety and depression are the most common comorbid psychiatric disorders of CRF.[39] Often, fatigue is the final common pathway for a range of physical and emotional etiologies.

Depression can be a comorbid, disabling syndrome that affects approximately 15% to 25% of persons with cancer.[40] The presence of depression, as manifested by loss of interest, difficulty concentrating, lethargy, and feelings of hopelessness, can compound the physical causes for fatigue in these individuals and persist long past the time when physical causes have resolved.[41]

Anxiety and fear associated with a cancer diagnosis, as well as its impact on the person's physical, psychosocial, and financial well-being, are sources of emotional stress. Distress associated with the diagnosis of cancer alone may trigger fatigue. A study of 74 early-stage breast cancer patients with no history of affective disorder assessed various symptoms of adjustment approximately 2 weeks after diagnosis; about 45% noted moderate or high levels of fatigue. This fatigue may have been secondary to the increased cognitive strain of dealing with the diagnosis or to insomnia, reported as moderate to severe by about 60% of the patients. Therefore, fatigue may begin before treatment as a result of worry or other cognitive factors, both primary and secondary to insomnia. Various forms of treatment may compound this fatigue.[42]

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