An infection occurs when harmful bacteria, viruses, or fungi (such as yeast) invade the body and the immune system is not able to destroy them quickly enough. People with cancer are more likely to develop infections because both cancer and cancer treatments can weaken your immune system.

The immune system

The immune system fights harmful organisms (bacteria, viruses, and fungi) that try to invade the body. The immune system includes the skin, the spleen, the lymph nodes, and the bone marrow (a spongy, fatty tissue found inside larger bones). It also includes leukocytes, the infection-fighting white blood cells (WBCs) that are made inside the bone marrow. If not enough WBCs are present, a condition called leukopenia results, and the body is less able to fight an infection. Some WBCs, called neutrophils, are able to destroy harmful bacteria. A low level of neutrophils, called neutropenia, can increase the risk of dangerous bacterial infections.

Causes

Cancer and cancer treatment can interfere with the functioning of the immune system in several ways:

• Because the immune system is busy fighting the cancer, it is less able to protect against other infections at the same time.
  
  
• Lack of sleep, stress, poor diet, and other side effects of cancer and cancer treatment may weaken the immune system.
  
  
• Chemotherapy may cause the bone marrow and other parts of the immune system to malfunction, lowering the production of WBCs.
  
  
• Radiation therapy can also affect the bone marrow, especially if given to extensive areas of the body or to bones in the pelvis, legs, chest, or abdomen.
  
  
• Cancers that affect the bone marrow directly (including leukemia or lymphoma) or cancers that metastasize (spread) to the bone (such breast or lung cancers) can crowd normal bone marrow cells, lowering WBC production.

Signs and symptoms

People with cancer and neutropenia or a low WBC count are at risk for having a minor infection become serious. Infections can start almost anywhere, but common places include the mouth, skin, lungs, urinary tract, rectum, and genital areas (such as the vagina). Talk to your doctor right away if you experience any of the following signs of infection:

• A fever (temperature of 100.5°F or higher)
  
  
• Chills or sweating
  
  
• Sore throat or sores in the mouth
  
  
• Abdominal pain
  
  
• Pain or burning when urinating or frequent urination
  
  
• Diarrhea or sores around the anus
  
  
• A cough or shortness of breath
  
  
• Any redness, swelling, or pain, particularly around a cut or wound
  
  
• Unusual vaginal discharge or itching

Treatment

If a person has neutropenia or their overall WBC count is low, the doctor may decide to treat the conditions with medications, such as filgrastim (Neupogen), pegfilgrastim (Neulasta), or sargramostim (Leukine or Prokine) to encourage the body to make more neutrophils or other types of WBCs to reduce the risk of an infection. Learn more about ASCO’s recommendations for white blood cell growth factors.

If an infection occurs, patients may be treated with antibiotics or antifungal medications. If neutropenia and a fever develop together (called neutropenic fever), patients may need to be hospitalized in order to receive intravenous (IV) antibiotics. Patients at high risk for developing an infection, because of neutropenia or because of chemotherapy or radiation therapy, may be treated with prophylactic (preventive) antibiotics or antifungal medications.

Tips for preventing infections

In addition to receiving treatment from your doctor, the following suggestions can help prevent infections:

• Get plenty of rest and eat a well-balanced diet.
  
  
• Try to avoid crowded places and contact with people who are ill.
  
  
• Do not share food, drink cups, utensils, or other personal items, such as toothbrushes.
  
  
• Wash your hands frequently, especially after using the bathroom or before eating.
  
  
• Shower or bathe daily and use lotion to prevent your skin from becoming dry and cracked.
  
  
• Be careful using sharp objects, such as scissors or knives, and use an electric shaver to avoid cuts.
  
  
• Do not eat raw foods, including meats, shellfish, and eggs, and avoid or carefully wash raw fruits and vegetables.
  
  
• Do not change cat litter or handle animal waste.
  
  
• Use gloves for gardening and housework, especially while cleaning.
  
  
• Clean your teeth and gums with a soft toothbrush and, if your doctor or dentist recommends one, use a mouthwash to prevent infections.

More Information

Managing Side Effects

Last Updated: April 27, 2009