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. Chronic fatigue syndrome describes prolonged debilitating fatigue that may persist or relapse, and is not related to cancer. Fatigue related to cancer is called chronic because it lasts over a period of time and is not completely relieved by sleep and rest. Chronic fatigue diagnosed in patients with cancer may be called "cancer fatigue", "cancer-related fatigue", or "cancer treatment-related fatigue". 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, family care, and relationships with others, and whether he or she continues with cancer treatment. Patients receiving some cancer treatments may miss work or school, withdraw from friends, need more sleep, and, in some cases, may not be able to think clearly or 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.

How long fatigue lasts and how much fatigue the patient feels depends on the type and schedule of cancer treatment. For example, patients treated with cycles of chemotherapy usually have the most fatigue in the days following treatment, then less fatigue until the next treatment. Patients treated with external-beam radiation therapy usually have more fatigue as their treatment continues. It is likely that most patients beginning cancer treatment already feel fatigued following diagnostic tests, surgery, and the emotional distress of coping with a cancer diagnosis.

Glossary Terms

The tasks of everyday life. These activities include eating, dressing, getting into or out of a bed or chair, taking a bath or shower, and using the toilet. Instrumental activities of daily living are activities related to independent living and include preparing meals, managing money, shopping, doing housework, and using a telephone. Also called ADL.

Symptoms or signs that begin and worsen quickly; not chronic.

Weakness; lack of energy and strength.

Pertaining to biology or to life and living things. In medicine, refers to a substance made from a living organism or its products. Biologicals may be used to prevent, diagnose, treat or relieve of symptoms of a disease. For example, antibodies, interleukins, and vaccines are biologicals. Biological also refers to parents and children who are related by blood.

A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.

Treatment with drugs that kill cancer cells.

A disease or condition that persists or progresses over a long period of time.

A condition lasting for more than 6 months in which a person feels tired most of the time and may have trouble concentrating and carrying out daily activities. Other symptoms include sore throat, fever, muscle weakness, headache, and joint pain. Also called CFS.

To adjust to new situations and overcome problems.

The process of identifying a disease, such as cancer, from its signs and symptoms.

A specific test or series of steps done to help diagnose a disease or condition. Mammograms and colonscopies are examples of diagnostic procedures.

Extreme mental or physical pain or suffering.

A type of radiation therapy that uses a machine to aim high-energy rays at the cancer from outside of the body. Also called external radiation therapy.

A condition marked by extreme tiredness and inability to function due lack of energy. Fatigue may be acute or chronic.

A feeling of tiredness, weakness, and lack of interest in daily activities.

A condition in which a person is so tired or weak that he or she is unable to do anything.

Having to do with how the mind works and how thoughts and feelings affect behavior.

The return of signs and symptoms of cancer after a period of improvement.

In clinical trials, the step-by-step plan for how patients are to be treated; for example, the drug or type of radiation therapy that is to be given, the method by which it is to be given, the amount of time between courses, and the total length of treatment.

A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.

An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.