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Fever, Sweats, and Hot Flashes (Patient)


Fever, sweats, or hot flashes may be side effects of cancer or its treatment.

In patients with cancer, fever may be caused by infection, a tumor, or reactions to drugs or blood transfusions.

Sweating is the body's way of lowering body temperature by causing heat loss through the skin. In patients with cancer, sweating may be caused by fever, a tumor, or cancer treatment.

Hot flashes can also cause too much sweating. They may occur in natural menopause or in patients who have been treated for breast cancer or prostate cancer.

Fever, sweats, and hot flashes affect quality of life in many patients with cancer.

A treatment plan to help manage fever, sweats, or hot flashes is based on the patient's condition and goals of care. For some patients, relieving symptoms and improving quality of life is a more important goal than treating the fever to prolong life.

This summary describes the causes and treatment of fever, sweats, and hot flashes in cancer patients.

Causes of Fever in Patients with Cancer

Fever is a rise in body temperature caused by the body's response to illness.

Normal human body temperature changes during each 24-hour period according to a definite pattern. It is lowest in the morning before dawn and highest in the afternoon. Temperature control actions in the body keep the amount of heat that is made equal to the amount lost. This keeps body temperature normal.

An abnormal rise in body temperature is caused by either a condition called hyperthermia or fever. Hyperthermia is caused by a breakdown in the body's temperature control actions. In fever, the temperature controls in the body are working as they should, but body temperature rises as the body responds to illness.

There are three phases of fever:

  • In the first phase, body temperature rises as blood vessels in the skin narrow. This prevents heat from leaving the body through the skin. The skin becomes cool, the muscles contract and cause shivering or chills, and the body makes more heat. The body continues to make and keep heat until a new, higher temperature is reached.
  • In the second phase, a new, higher temperature has been reached. The amount of heat the body makes and loses is the same. Shivering stops, and the body stays at the new, higher temperature.
  • In the third phase, body temperature falls to normal as blood vessels in the skin open and move blood from inside the body to the skin surface. This helps get rid of extra heat. Sweating occurs and helps to cool the body.

Certain problems are more likely in older people or the very young. In older people, the temperature control centers in the brain may not work the way they should and can lead to hyperthermia. This may cause irregular heartbeat, lack of blood flow to parts of the body, confusion, or heart failure. In children between 6 months and 6 years old, high fever may lead to seizures.

There are many possible causes of fever in patients with cancer.

The main causes of fever in patients with cancer are reactions to:

  • Infection.
  • Substances made by tumor cells.
  • Medicines, including:
  • Blood transfusions.
  • Graft-versus host disease, which occurs when a donor's transplanted tissue attacks the patient's tissue.

Other causes of fever in cancer patients include:

  • Drug withdrawal.
  • Neuroleptic malignant syndrome (NMS).
  • Blockages of the bladder, bowel, or kidney.
  • Treatment to stop blood flow to a tumor.
  • Blood clots.
  • Connective tissue disorders.
  • Brain hemorrhage or stroke.

Patients with fever need to be checked carefully for signs of infection.

The doctor will ask questions about past medical problems, check all medicines the patient is taking, and do a physical exam to look for the cause of fever. Patients, especially those who have fever and neutropenia (a very low white blood cell count), will have a complete checkup for signs of infection. Some of the areas the doctor will check include:

  • The skin and skin folds (for example, the breasts, armpits, or groin).
  • Body openings (mouth, ears, nose, throat, urethra, vagina, and rectum).
  • Areas on the skin where needles have been put in or biopsies have been done.
  • The teeth, gums, tongue, nose, throat, and sinuses.
  • Areas where lines into veins or arteries have been placed.
  • Areas where tubes have been placed, such as stomach tubes.
  • Samples of urine, sputum, and blood.

Patients with neutropenia may not show the usual signs of infection. These patients need to be checked often and should see their doctor if they have a fever.

eMedicineHealth Public Information from the National Cancer Institute

This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at or call 1-800-4-CANCER

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Some material in CancerNet™ is from copyrighted publications of the respective copyright claimants. Users of CancerNet™ are referred to the publication data appearing in the bibliographic citations, as well as to the copyright notices appearing in the original publication, all of which are hereby incorporated by reference.

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