Causes The causes of fatigue in people with cancer are not known. Fatigue commonly is an indicator of disease progression and is frequently one of the first symptoms of cancer in both children and adults. For example, parents of a child diagnosed with acute lymphocytic leukemia or non-Hodgkin's lymphoma frequently seek medical care because of the child's extreme fatigue. Tumors can cause fatigue directly or indirectly by spreading to the bone marrow, causing anemia, and by forming toxic substances in the body that interfere with normal cell functions. People who are having problems breathing, another symptom of some cancers, may also experience fatigue.
Fatigue can occur for many reasons.
The extreme stress that people with cancer experience over a long period of time can cause them to use more energy, leading to fatigue. However, there may be other reasons that cancer patients suffer from fatigue. Medication to treat pain, depression, vomiting, seizures, and other problems related to cancer may also cause fatigue. TNF may cause a decrease in protein stores in muscles causing the body to work harder to perform normal functions, and therefore causing fatigue. It is not always possible to determine the factors that cause fatigue in patients with cancer.