Childhood Leukemia: Cancer of the White Blood Cells

Leukemia refers to any of the various bone marrow cancers that cause large numbers of abnormal white blood cells to build up in the bloodstream. White blood cells normally help the immune system, but the abnormal white blood cells reproduce faster than normal white blood cells and other normal blood cells, and "crowd out" healthy blood cells. Resulting blood count imbalances can be detected in blood test results.

Children and Leukemia

Leukemia is the most common type of childhood cancer, accounting for 25 percent of all pediatric cancer cases. Most childhood bone marrow cancers are diagnosed when children are between the ages of two and eight.

Leukemia Symptoms and White Blood Cells

As bone marrow produces increasing numbers of white blood cells, a number of leukemia symptoms develop. When abnormal white blood cells increase, healthy blood cell levels drop, resulting in leukemia symptoms such as anemia and bleeding problems.

White blood cells are important disease fighters. While bone marrow affected by leukemia still produces white blood cells, the cells don't mature properly and can't fight infections effectively. Therefore, a heightened risk of infection is one of the most common leukemia symptoms.

Other common leukemia symptoms include:

  • bone pain
  • easy bruising
  • fatigue
  • joint pain
  • loss of appetite
  • nosebleeds
  • paleness.

While leukemia originates in bone marrow, abnormal white blood cells can metastasize, or spread, to other organs of the body, including the lymph nodes, brain, liver and testes. Depending on their location, further leukemia symptoms may develop.

Swollen lymph nodes are possible leukemia symptoms. If symptoms affect the chest's lymph nodes, symptoms may include breathing difficulties and blood circulation problems.

If leukemia spreads from the bone marrow to the brain, leukemia symptoms may include headaches and seizures. Vision problems and balancing difficulties may also occur.

Chronic and Acute Leukemia

Leukemia is classified as chronic or acute. Rapid accumulations of abnormal white blood cells and leukemia symptoms characterize acute leukemia. Chronic leukemia has a slower rate of white blood cell production, and symptoms are slower to develop.
 
Chronic leukemia can occur in children, but incidence rates are very low; fewer than 50 pediatric cases of chronic leukemia are reported annually in the United States. Approximately 98 percent of pediatric leukemia cases are acute varieties of the disease.

Acute Lymphocytic Leukemia

Acute lymphocytic leukemia, or ALL, accounts for 60 percent of acute leukemia cases in children. ALL gets its name because the bone marrow produces abnormal lymphocytes, a specific variety of white blood cells.

Acute lymphocytic leukemia symptoms usually develop when children are between the ages of two and eight, with most pediatric ALL cases diagnosed by age four. Boys are more likely to develop ALL than girls, and Caucasians appear to be at higher risk than other ethnicities.

Acute lymphocytic leukemia is more likely to affect lymph nodes in the chest than other acute varieties of leukemia. Metastasis of the cancer to the brain occurs in approximately six percent of all acute lymphocytic leukemia cases.

Acute Myelogenous Leukemia

Acute myelogenous leukemia, also known as acute nonlymphocytic leukemia, refers to acute leukemia that involves white blood cells other than lymphocytes. Instead, acute myelogenous leukemia (AML) affects a group of white blood cells called granulocytes. Approximately 38 percent of pediatric leukemia is classified as AML.
 
Acute myelogenous leukemia symptoms are not common in young children. The disease may occur in the first months after birth, after which it's rare until the teenage years. AML does have a greater chance of metastasis to the brain than ALL: 12 percent of acute myelogenous leukemia cases show symptoms of brain involvement.

Leukemia Diagnosis

If symptoms suggest leukemia, diagnosis begins with a thorough physical examination and evaluation of blood test results. The physical exam checks for common leukemia symptoms such as anemia, infection and bleeding problems.

Blood tests include a complete blood count to determine levels of white blood cells. If blood test results reveal discrepancies in white blood cell levels, a bone marrow biopsy can help confirm a leukemia diagnosis. An aspiration biopsy uses a long needle to gather samples of bone marrow. The back of the hip is the usual location for a bone marrow biopsy.

The bone marrow biopsy is examined microscopically for signs of abnormal white blood cells. If blood test results and bone marrow biopsies confirm leukemia, additional lymph node biopsies may be required to determine whether the cancer has spread. A spinal tap can determine whether the leukemia has spread to the central nervous system.

Leukemia Treatment

Chemotherapy medications are the first line of leukemia treatment. Chemotherapy drugs are systemic medications, meaning they affect the entire body. They kill fast-growing cells, such as leukemia's abnormal white blood cells.

Chemotherapy action kills fast-growing cells, but it also affects non-cancerous cells in the body. As a result, chemotherapy can cause a number of side effects, including:

  • anemia
  • easy bleeding
  • hair loss
  • increased infections
  • kidney damage
  • liver damage
  • nausea
  • skin color changes
  • vomiting.

To prevent the spread of leukemia to the central nervous system, intrathecal chemotherapy may be employed. During intrathecal therapy, chemotherapy drugs are administered to the cerebrospinal fluid surrounding the brain and spinal cord. High-risk patients may receive radiation therapy in addition to chemotherapy.

In advanced cases of leukemia, bone marrow transplants may be employed. Healthy bone marrow either from a donor or leukemia-free bone marrow harvested from the child's own body is transplanted into bone marrow affected by leukemia. Ideally, the introduced bone marrow functions normally and produces healthy white blood cells capable of fighting infections.

Leukemia Symptoms and Remission

The goal of leukemia treatment is remission: the absence of abnormal white blood cells and leukemia symptoms. Acute lymphocytic leukemia has a remission rate of more than 90 percent.
 
Once remission is achieved, the child requires maintenance chemotherapy for two or three years. Maintenance chemotherapy helps to prevent the leukemia from relapsing, or returning. Without maintenance treatment, most leukemia patients relapse.

Places to Find Help

Leukemia requires specialized care for successful treatment. Three outstanding leukemia treatment facilities are available in the United States:
  • Children's Oncology Group
  • Dana-Farber Cancer Center
  • Saint Jude's Children's Research Center.

Resources

American Cancer Society (2007). Overview: Leukemia – Children’s. Retrieved September 4, 2007, from the ACS Web site: http://www.cancer.org/docroot/CRI/content/CRI_2_2_1X_
What_is_leukemia_24.asp.

National Library of Medicine (2007). Leukemia, Childhood. Retrieved September 4, 2007, from the NLM Web site: http://www.nlm.nih.gov/medlineplus/leukemiachildhood.html.

Nemours Foundation (2005). Childhood cancer: Leukemia. Retrieved September 4, 2007, from the Nemours Foundation Web site: http://www.kidshealth.org/parent/medical/cancer/cancer_
leukemia.html.