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Fatigue (PDQ®): Supportive care - Patient Information [NCI] - Causes of Fatigue in Cancer Patients

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Fatigue caused by radiation therapy

Many patients receiving radiation therapy have fatigue that keeps them from being as active as they want to be. After radiation therapy begins, fatigue usually increases until mid-way through the course of treatments and then stays about the same until treatment ends. For many patients, fatigue improves after radiation therapy stops. However, in some patients, fatigue will last months or years after treatment ends. Some patients never have the same amount of energy they had before treatment.

Cancer-related fatigue has been studied in patients with breast cancer and prostate cancer. The amount of fatigue they felt and the time of day the fatigue was worst was different in different patients.

In men with prostate cancer, fatigue was increased by having the following symptoms before radiation therapy started:

  • Poor sleep.
  • Depression.

In women with breast cancer, fatigue was increased by the following:

  • Working while receiving radiation therapy.
  • Having children at home.
  • Depression.
  • Anxiety.
  • Trouble sleeping.
  • Younger age.
  • Being underweight.
  • Having advanced cancer or other medical conditions.

Fatigue caused by biologic therapy

Biologic therapy often causes flu-like symptoms. These symptoms include being tired physically and mentally, fever, chills, muscle pain, headache, and not feeling well in general. Some patients may also have problems thinking clearly. Fatigue symptoms depend on the type of biologic therapy used.

Fatigue caused by surgery

Fatigue is often a side effect of surgery, but patients usually feel better with time. However, fatigue caused by surgery can be worse when the surgery is combined with other cancer treatments.

Anemia is a common cause of fatigue.

Anemia affects the patient's energy level and quality of life. Anemia may be caused by the following:

  • The cancer.
  • Cancer treatments.
  • A medical condition not related to the cancer.

The effects of anemia on a patient depend on the following:

  • How quickly the anemia occurs.
  • The patient's age.
  • The amount of plasma (fluid part of the blood) in the patient's blood.
  • Other medical conditions the patient has.

Side effects related to nutrition may cause or increase fatigue.

The body's energy comes from food. Fatigue may occur if the body does not take in enough food to give the body the energy it needs. For many patients, the effects of cancer and cancer treatments make it hard to eat well. In people with cancer, three major factors may affect nutrition:

  • A change in the way the body is able to use food. A patient may eat the same amount as before having cancer, but the body may not be able to absorb and use all the nutrients from the food. This is caused by the cancer or its treatment.
  • A decrease in the amount of food eaten because of low appetite, nausea, vomiting, diarrhea, or a blocked bowel.
  • An increase in the amount of energy needed by the body because of a growing tumor, infection, fever, or shortness of breath.
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WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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