Understand Childhood Cancers and Blood Disorders
Infections in the Cancer Patient
One of the major problems faced by a child with cancer is that of infection. The most important contributing factor to infections is a low white cell count, particularly the neutrophil, the most powerful infection fighting cell. Neutrophils, produced in the bone marrow, can be low when the malignant cells replace the normal bone marrow elements, as seen in leukemia and neuroblastoma, or when the marrow is suppressed by chemotherapy. Several cancers, steroids and many chemotherapy drugs can suppress the body's immune system and antibody production, further increasing the infection risk. A breach in the body's normal outer barriers, as seen with mouth sores caused by chemotherapy or with external catheters, allows germs to enter the blood stream. Any foreign body, such as central venous catheters or shunts, can become a site for germs to settle and proliferate. Obstruction of internal organs such as the airway or urinary tract, can allow germs to accumulate and grow. Severe diarrhea can erode the lining of the intestinal tract, allowing normally benign germs to penetrate the bowel wall, leading to potentially life-threatening peritonitis. Patients who undergo stem cell transplant are left with no functioning immune system for a prolonged period of time.
Virtually every type of germ has been found to cause infections in children with cancer. Bacterial infections are the most common and often most serious infections encountered, particularly when appearing as blood infections known as sepsis. Sepsis can cause fevers, low blood pressure (shock), and serious respiratory distress. Intestinal bacteria, including E.Coli, Klebsiella, and Pseudomonas, are particularly dangerous when they enter the blood stream. Usually harmless bacteria that normally reside on the skin can also cause major problems when entering the body. To complicate the picture, multiple courses of antibiotics will often promote the development of antibiotic-resistant bacteria.
Fungus is another group of germs that commonly infect children with cancer. Candida will appear as a painful mouth infection called thrush, with a white coating of the tongue; the fungus can spread to nearly all internal organs, particularly the brain, lung, liver, and spleen. Aspergillus is a difficult infection that affects all parts of the respiratory system, from the sinuses to the lungs.
Viruses that usually cause mild illness in healthy people can be deadly in patients with impaired defense mechanisms. Chickenpox can cause a lethal pneumonia or liver failure. Herpes viruses, mere annoyances in the normal population, can cause serious organ failure in immune suppressed children. Cytomegalovirus is a special challenge faced by stem cell transplant patients, with potential for severe liver and lung damage.
Finally, a number of parasites can cause serious problems in this patient population. Pneumocystis Carinii has been a particularly troublesome problem, causing pneumonia in patients with leukemia and lymphoma, as well as any patients on prolonged steroid therapy. Toxoplasmosis and Cryptosporidium are uncommon parasites that can cause serious problems in patients with immune difficulties.
Many prophylactic measures have had a major impact in decreasing the risk of these infections. Strict hand-washing between patient contacts is probably the most important preventive measure that one can take and cannot be emphasized enough. Medical staff in particular are encouraged to always wash their hands with effective antiseptic soap between examining patients. Likewise, it is important to restrict at-risk patients from having contact with people with communicable illnesses, particularly people who are having respiratory symptoms (cough, sneezing, runny noses) that might indicate a high risk of spreading a respiratory illness. Scrupulous preparation prior to accessing any central lines is very important to prevent line infections that can lead to serious consequences.
For many types of cancer, prophylactic antibiotics play an important role in preventing infections. Virtually all patients with acute leukemia, as well as many with lymphoma and others treated with long courses of corticosteroids (such as children with brain tumors) are treated with Bactrim, a sulfa drug that is very effective in preventing Pneumocystis pneumonia. For those who cannot tolerate Bactrim, substitution with Pentamidine or Dapsone is recommended. Fungal prophylaxis with nystatin or fluconazole is helpful for patients with leukemia. Patients who are undergoing stem cell transplant may benefit from acyclovir and later generation drugs to prevent Herpes infections. Varicella vaccine should be considered for patients who will be immunocompromised, although its use in patients in active treatment is somewhat controversial.
An important point to remember is that fever in a child with an increased risk of infections is an absolute red flag, as some of these infections can rapidly become life-threatening. Whenever there is a fever present, the child's physician should be contacted immediately, and the doctor will then determine the amount of risk and appropriate management. Sometimes there will be no emergency issue and phone contacts might be sufficient, but it's best to let the doctor determine the proper course of action. At times an infection will not be accompanied by fever - either because of the nature of the infection, or in the presence of corticosteroids which can mask fevers. In these situations, should there be some other symptom, such as unexplained pain, respiratory or gastrointestinal complaints - a physician should be consulted as well.