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- • Changes in energy production and the availability of nutrients may cause fatigue. The tumor itself may make
- the body function in an overactive or "hypermetabolic" state, for example. Tumor cells compete for nutrients,
- often at the expense of normal cells' growth and metabolism. Weight loss, reduced appetite and fatigue are often
- the result.
- • Also associated with fatigue are diagnostic tests, anesthesia, surgery, radiation therapy , chemotherapy , and
- drugs used to control symptoms and side effects such as nausea, vomiting, pain and insomnia.
- • Eighty to 96 percent of all chemotherapy patients experience fatigue.
- • Drugs such as vincristine and vinblastine may cause fatigue because of their toxic effects on nerves
- (neurotoxicity). With cisplatin , low magnesium levels, along with neuorotoxicity, may cause fatigue.
- • Fatigue that increases over time (cumulative fatigue) occurs in radiotherapy patients regardless of treatment
- site. This usually improves within one month but may last up to three months after treatment stops.
- • Fatigue may become so severe during certain treatments that dosages may be limited.
- • As cancer cells die in response to therapy, certain substances are released that may contribute to fatigue. More
- attention has recently been paid to the possible role of cytokines in the development of fatigue. Cytokines are
- natural cell products or proteins, such as the interferons and interleukins , that are normally released by white
- blood cells , lymphocytes and macrophages in response to infection. These cytokines carry messages that
- regulate other elements of the immune and neuroendocrine systems. In high amounts, these cytokines can be
- toxic and lead to persistent fatigue.
