This patient summary on fatigue is adapted from a summary written for health professionals by cancer experts. This and other credible information about cancer treatment, screening, prevention, supportive care, and ongoing clinical trials is available from the National Cancer Institute. Fatigue is one of the most common complaints of people diagnosed with cancer and cancer survivors. This brief summary describes fatigue, its causes and treatment.

Fatigue occurs in 14% to 96% of people with cancer, especially those receiving treatment for their cancer. Fatigue is complex, and has biological, psychological, and behavioral causes. Fatigue is difficult to describe and people with cancer may express it in different ways, such as saying they feel tired, weak, exhausted, weary, worn-out, heavy, or slow. Health professionals may use terms such as asthenia, fatigue, lassitude, prostration, exercise intolerance, lack of energy, and weakness to describe fatigue.

Fatigue can be described as a condition that causes distress and decreased ability to function due to a lack of energy. Specific symptoms may be physical, psychological, or emotional. To be treated effectively, fatigue related to cancer and cancer treatment needs to be distinguished from other kinds of fatigue.

Fatigue may be acute or chronic. Acute fatigue is normal tiredness with occasional symptoms that begin quickly and last for a short time. Rest may alleviate fatigue and allow a return to a normal level of functioning in a healthy individual, but this ability is diminished in people who have cancer. Chronic fatigue is long lasting. Chronic fatigue syndrome describes prolonged debilitating fatigue that may persist or relapse. This illness is sometimes diagnosed in people who do not have cancer. Although many treatment- and disease-related factors may cause fatigue, the exact process of fatigue in people with cancer is not known.

Fatigue can become a very important issue in the life of a person with cancer. It may affect how the person feels about him- or herself, his or her daily activities and relationships with others, and whether he or she continues with cancer treatment. Patients receiving some cancer treatments may miss work, withdraw from friends, need more sleep, and, in some cases, may not be able to perform any physical activities because of fatigue. Finances can become difficult if people with fatigue need to take disability leave or stop working completely. Job loss may result in the loss of health insurance or the inability to get medical care. Understanding fatigue and its causes is important in determining effective treatment and in helping people with cancer cope with fatigue. Tests that measure the level of fatigue have been developed.

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. The central nervous system (the brain and spinal cord) may be affected by the cancer or the cancer therapy (especially biological therapy) and cause fatigue. Medication to treat pain, depression, vomiting, seizures, and other problems related to cancer may also cause fatigue. Tumor necrosis factor (TNF) is a substance that can be produced by a tumor, or may be given to a patient as a treatment for some types of cancer. TNF may cause a decrease in protein stores in muscles causing the body to work harder to perform normal functions, and therefore causing fatigue. There are many chemical, physical, and behavioral factors that are thought to cause fatigue.

Factors Related to Fatigue

It is not always possible to determine the factors that cause fatigue in patients with cancer. Possible factors include the following:

• Cancer treatment.
• Anemia.
• Medications.
• Weight loss and loss of appetite.
• Changes in metabolism.
• Decreased levels of hormones.
• Emotional distress.
• Difficulty sleeping.
• Inactivity.
• Difficulty breathing.
• Loss of strength and muscle coordination.
• Pain.
• Infection.
• Having other medical conditions in addition to cancer.

Cancer treatment

Fatigue is a common symptom following radiation therapy or chemotherapy. It may be caused by anemia, or the collection of toxic substances produced by cells. In the case of radiation, it may be caused by the increased energy needed to repair damaged skin tissue.

Several factors have been linked with fatigue caused by chemotherapy. Some people may respond to the diagnosis and treatment of cancer with mood changes and disrupted sleep patterns. Nausea, vomiting, chronic pain, and weight loss can also cause fatigue.

Fatigue has long been associated with radiation therapy although the connection between them is not well understood. Fatigue usually lessens after the therapy is completed, although not all patients return to their normal level of energy. Patients who are older, have advanced disease, or receive combination therapy (for example, chemotherapy plus radiation therapy) are at a higher risk for developing long-term fatigue.

Biological therapy frequently causes fatigue. In this setting, fatigue is one of a group of side effects known as flulike syndrome. This syndrome also includes fever, chills, muscle pain, headache, and a sense of generally not feeling well. Some patients may also experience problems with their ability to think clearly. The type of biological therapy used may determine the type and pattern of fatigue experienced.

Many people with cancer undergo surgery for diagnosis or treatment. Fatigue is a problem following surgery, but fatigue from surgery improves with time. It can be made worse, however, when combined with the fatigue caused by other cancer treatments.

Anemia

Anemia may be a major factor in cancer-related fatigue and quality of life in people with cancer. Anemia may be caused by the cancer, cancer treatment, or may be related to other medical causes.

Nutrition factors

Fatigue often occurs when the body needs more energy than the amount being supplied from the patient's diet. In people with cancer, 3 major factors may be involved: a change in the body's ability to process food normally, an increased need by the body for energy (due to tumor growth, infection, fever, or problems with breathing), and a decrease in the amount of food eaten (due to lack of appetite, nausea, vomiting, diarrhea, or bowel obstruction).

Psychological factors

The moods, beliefs, attitudes, and reactions to stress of people with cancer can contribute to the development of fatigue. Approximately 40% to 60% of the cases of fatigue among all patients (cancer patients as well as other patients) are not caused by disease or other physical reasons. Anxiety and depression are the most common psychological disorders that cause fatigue.

Depression may be a disabling illness that affects approximately 15% to 25% of people who have cancer. When patients experience depression (loss of interest, difficulty concentrating, mental and physical tiredness, and feelings of hopelessness), the fatigue from physical causes can become worse and last longer than usual, even after the physical causes are gone. Anxiety and fear associated with a cancer diagnosis, as well as its impact on a person's physical, mental, social, and financial well-being are sources of emotional stress. Distress from being diagnosed with cancer may be all that is needed to trigger fatigue.

Mental ability factors

Decreased attention span and difficulty understanding and thinking are often associated with fatigue. Attention problems are common during and after cancer treatment. Attention may be restored by activities that encourage rest. Sleep is also necessary for relieving attention problems but it is not always enough.

Sleep disorders and inactivity

Disrupted sleep, poor sleep habits, less sleep at night, sleeping a lot during the day, or no activity during the day may contribute to cancer-related fatigue. Patients who are less active during the daytime and awaken frequently during the night report higher levels of cancer-related fatigue.

Tags: Cancer, Chronic Fatigue Syndrome and Fibromyalgia

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