What is fatigue?

Fatigue can be confused with tiredness. Everyone gets tired. In fact, it is an expected feeling after certain activities or at the end of the day. Usually, we know why we're tired and a good night's sleep will solve the problem.

Fatigue is less precise, less cause-and-effect. Fatigue is a daily lack of energy; an unusual or excessive whole-body tiredness, not relieved by sleep. It can be acute (lasting a month or less) or chronic (lasting from 1 month to 6 months or longer). Fatigue can have a profound negative impact on a person's ability to function and quality of life.

Cancer-related fatigue (CRF - sometimes simply called "cancer fatigue") is one of the most common side effects of cancer and its treatments. It is often described as "paralyzing." Usually, it comes on suddenly, does not result from activity or exertion, and is not relieved by rest or sleep. It may not end - even when treatment is complete.

The exact reason for cancer fatigue is unknown. CRF may be related to both the disease process and treatments, including surgery, chemotherapy, and radiation therapy. Cancer treatments commonly associated with CRF are:

  • Chemotherapy. Any chemotherapy drug may result in fatigue. This may vary from person to person. Some people say it lasts only a couple of days. Others feel the CRF persists through and beyond completion of treatment. Drugs such as vincristine, vinblastine, and cisplatin often cause CRF.
  • Radiation therapy. Radiation therapy can cause cumulative fatigue (fatigue that increases over time). This can occur regardless of treatment site. CRF usually lasts from 3-4 weeks after treatment stops, but can continue for up to 2-3 months.
  • Bone marrow transplant. This aggressive form of treatment can cause CRF that lasts up to one year.
  • Biologic therapy. Cytokines are natural cell proteins, such as interferons and interleukins, that are normally released by white blood cells in response to infection. These cytokines carry messages that regulate other elements of the immune and endocrine systems. In high amounts, these cytokines can be toxic and lead to persistent fatigue.
  • Anemia. Anemia can result from blood counts that are reduced by treatments reducing the oxygen-carrying ability (hemoglobin) of the blood. About 7 in 10 patients experience anemia during chemotherapy.
  • Combination therapy. Patients experiencing more than one treatment at the same time or one after the other may experience more CRF.
  • Tumor-induced "hypermetabolic" state. Tumor cells compete for nutrients, often at the expense of the normal cell's growth and metabolism. Weight loss, decreased appetite, and fatigue are common results.
  • Decreased nutrition from the side effects of treatments (i.e., nausea, vomiting, mouth sores, taste changes, heartburn, and diarrhea).
  • Hypothyroidism. If the thyroid gland is underactive, metabolism may slow down so that the body does not burn food fast enough to provide adequate energy. This is a common condition in general but may happen after radiation therapy to the lymph nodes in the neck.
  • Medications used to treat side effects such as nausea, pain, depression, anxiety, and seizures can contribute to CRF.
  • Pain. Research shows that chronic, severe pain increases fatigue.
  • Many patients try to maintain their normal daily routine and activities during treatments. Modification may be necessary in order to conserve energy.
  • Stress can worsen feelings of fatigue. This can include any type of stress: from dealing with the disease and the unknowns to worrying about daily accomplishments to worrying about not meeting the expectations of others.
  • Depression and fatigue often go hand in hand. It may not be clear as to which started first. Families may be confused as well. One way to sort this out is to try to understand how much of a problem is caused by the depressed feelings. Are you depressed all the time? Were you depressed before your cancer diagnosis? Are you preoccupied with feeling worthless and useless? If the answers to these questions are yes, you may need treatment for depression.
  • Insomnia. Inability to sleep 8 hours a night will cause both mental and physical fatigue.