Cancer-related fatigue is common in cancer patients. Fatigue is often confused with tiredness. Tiredness happens to everyone -- it's a feeling you expect 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 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 you from functioning normally and impacts your quality of life.
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Cancer-related fatigue (CRF) 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 may continue even after treatment is complete.
What Causes CRF?
The exact reason for CRF is unknown, but it may be related to the disease process or its treatments.
The following cancer treatments are commonly associated with fatigue:
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 others say the problem persists throughout the course of treatment and even 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.
Hormone therapy can cause fatigue by depriving the body of estrogen. It can last throughout the course of treatment or longer.
Biological therapy. Interferons and interleukins are cytokines, natural cell proteins that are normally released by white blood cells in response to infection. In high amounts, these cytokines can lead to persistent fatigue.
Combination therapy. More than one cancer treatment at the same time or one after the other also increases the chances of developing fatigue.
What Other Factors Contribute To Fatigue?
Other factors which may contribute to fatigue include:
Tumor-induced "hypermetabolic" state. Tumor cells compete for nutrients, often at the expense of normal cells. In addition to fatigue, weight loss and decreased appetite are common effects.
Decreased nutrition from the side effects of treatments (such as nausea, vomiting, mouth sores, taste changes, heartburn, or diarrhea) can cause fatigue.
Cancer treatments can cause reduced blood cell counts that can lead to anemia, a blood disorder that occurs when there is not enough hemoglobin, a substance in red blood cells that enables the blood to transport oxygen through the body. When the blood cannot transport enough oxygen to the body, fatigue can result.
If the thyroid gland is under-active, 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 also happen after radiation therapy to the lymph nodes in the neck.
Medicines used to treat side effects such as nausea, pain, depression, anxiety and seizures can cause fatigue.
Less physical activity and mobility problems can lead to fatigue in older people. Younger people in treatment sometimes overexert themselves and bring on fatigue.
Hormonal changes related to medicine, including cancer medicines, can cause fatigue.
Chronic, severe pain increases fatigue.
Stress can worsen feelings of fatigue. Stress can result from dealing with the disease and its "unknowns," as well as from worrying about daily accomplishments or trying to meet the expectations of others. Fatigue often results when patients try to maintain their normal daily routines and activities during treatment. Modifying your activities can help conserve energy.
Depression and fatigue often go hand-in-hand, but it may not be clear which started first. One way to sort this out is to try to understand your depressed feelings and how they affect your life. If you are depressed all the time, were depressed before your cancer diagnosis, or are preoccupied with feeling worthless and useless, you may need treatment for depression.