Tiredness happens to everyone -- it is an expected feeling after certain activities or at the end of the day. Usually, you know why you are tired and a good night's sleep solves the problem.
Fatigue, in contrast to tiredness, 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 one month to six months or longer). Fatigue can prevent a person from functioning normally and impacts a person's quality of life.
Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the prevention and cessation of cigarette smoking and the control of tobacco use. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
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Fatigue is one of the most common side effects of cancer and its treatment. It is not predictable by tumor type, treatment, or stage of illness. Usually, it comes on suddenly, does not result from activity or exertion, and is not relieved by rest or sleep. It often is described as "paralyzing." It may continue even after treatment is complete.
What Causes Cancer-Related Fatigue?
The exact reason is unknown. Cancer-related fatigue may be related to the disease process or its treatments.
Cancer treatments commonly associated with fatigue include:
Chemotherapy. Any chemotherapy drug may cause fatigue. Patients frequently experience fatigue after several weeks of chemotherapy, but this varies among patients. In some patients, fatigue lasts a few days, while in others, it persists throughout and after the treatment is complete.
Radiation therapy.Radiation therapy can cause cumulative fatigue (fatigue that increases over time). This can occur regardless of the treatment site. Fatigue usually lasts from three to four weeks after treatment stops, but can continue for up to two to three months.
Biological therapy. Interferons and interleukins are cytokines, natural cell proteins 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.
Combination or sequential therapy. More than one cancer treatment at the same time or one after the other increases the chances of developing fatigue.