Leukemias

Childhood Leukemia

Leukemia is the most common childhood cancer. It is a cancer of the child’s bone marrow and blood. When children have leukemia, their bone marrow (the soft inner part of bones where new blood cells are made) makes white blood cells that do not mature properly and reproduce rapidly, crowding out healthy cells that normally mature into infection-fighting white blood cells, red blood cells, and blood platelets.

In most cases, the cancerous leukemia cells invade the bloodstream quickly and spread to other parts of the body, including the lymph nodes, liver, spleen, brain and spinal cord (the central nervous system), and the testicles in boys. Childhood leukemia most frequently occurs in children between the ages of 2 and 6 years old, but it can occur at any age.

The leukemia seen in children accounts for about 25% of all childhood cancers and affects an estimated 2,200 children every year. Fortunately, the cure rate is high and, with treatment, most children can achieve remission of disease (when cancer cells can no longer be found). The remission rate for some forms of childhood leukemia is as high as 90%.

Childhood leukemias are generally classified as either acute (developing rapidly) or chronic (developing slowly). About 98% of leukemias in children are acute leukemias. The most common forms of acute childhood leukemia are acute lymphocytic leukemia (ALL) and acute myelogenous leukemia (AML), depending on the types of white blood cells involved — lymphocytes or myelocytes.

Roughly 60% of children with leukemia have ALL and about 38% have AML. Chronic forms of the disease (chronic lymphocytic leukemia and chronic myelogenous leukemia) are very rare in children but much more common in adults. Another rare type of childhood leukemia, called juvenile myelomonocytic leukemia, occurs most often in children under 4 years old.

Risk Factors

Children who have an identical twin diagnosed with ALL or AML before age 6 have a 20% to 25% increased risk of developing either one of these leukemias. Fraternal twins and other siblings of children with leukemia are two to four times more likely than children in the general population of developing leukemia.

Children born with certain genetic disorders, such as Down syndrome, Klinefelter syndrome, Fanconi syndrome, neurofibromatosis, and ataxia telangiectasia, and children who receive drugs to suppress their immune systems after getting an organ transplant also have a higher risk of developing this disease.

Also at higher risk are children who previously received chemotherapy or radiation therapy as treatment for cancer, typically within the first eight years after treatment. Women who are pregnant or suspect they may be should inform their doctor before getting tests or procedures involving x-rays or other forms of radiation.

Symptoms and Diagnosis

Because children with leukemia do not have enough healthy white blood cells, they may be susceptible to fevers and recurrent infections. Since they do not have enough red blood cells, they may develop anemia with symptoms of fatigue (feeling tired), weakness and shortness of breath. Because they do not have enough blood platelets, they may bruise and bleed easily, have frequent nosebleeds or bleed for a long time even from a minor cut.

Other symptoms can include pain in their bones or joints that could cause a limp, poor appetite, swollen lymph nodes and abdominal discomfort caused by a swollen spleen or liver. Swollen lymph nodes in the chest can cause breathing problems and interfere with the flow of blood to and from the heart.

In about 12% of children with AML and 6% of children with ALL, the leukemia spreads to the brain and causes abnormal vision, headaches, problems with balance or seizures.

To diagnose leukemia, your child’s doctor will perform a physical exam to check for swollen lymph nodes and signs of infection, anemia, abnormal bleeding and an enlarged spleen or liver and take a family medical history. The doctor will also order a blood test called a complete blood count to count the number red cells, white cells and platelets in your child’s blood. He or she will also order an examination of a blood smear under a microscope to check for abnormal blood cells usually seen in children with leukemia.

Depending on the results of the blood tests, your child’s physician may order a bone marrow biopsy and aspiration in which samples of bone marrow and marrow fluid are removed for testing, a lymph node biopsy or a lumbar puncture (also called a spinal tap) in which fluid is removed from the child’s spine in the area of the lower back to see if the leukemia cells have spread to the spine or brain. Other tests may also be done, including genetic studies to determine features of the leukemia cells and distinguish the specific type of leukemia.

Treatment

Based on the information from diagnostic tests, your child’s doctor will generally prescribe chemotherapy or radiation therapy or both. The goal of treatment is to put your child’s cancer in remission. Once remission is achieved, a pediatric oncologist (a specialist in childhood cancer) will give maintenance chemotherapy in cycles over a period of two to three years to prevent the cancer from returning.

Sometimes a bone marrow transplant may be required instead of or in addition to chemotherapy. A bone marrow transplant involves infusion of healthy bone marrow into a child’s body.