The term leukemia refers to cancers of the white blood cells (also called leukocytes or WBCs). When someone has leukemia, large numbers of abnormal white blood cells are produced in the bone marrow. These abnormal white cells crowd the bone marrow and flood the bloodstream, but they cannot perform their proper role of protecting the body against disease because they are defective.
As leukemia progresses, the cancer interferes with the body's production of other types of blood cells, including red blood cells and platelets. This results in anemia (low numbers of red cells) and bleeding problems, in addition to the increased risk of infection caused by white cell abnormalities.
As a group, leukemias account for about 30% of all childhood cancers and affect more than 3,000 American young people each year. Luckily, the chances for a cure are very good with leukemia. With treatment, most children with leukemia will be free of the disease without it coming back.
Types of Leukemia
In general, leukemias are classified into acute (rapidly developing) and chronic (slowly developing) forms. In children, most leukemias are acute.
Acute childhood leukemias are also divided into acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), depending on whether specific white blood cells called lymphyocytes or myelocytes, which are linked to immune defenses, are involved.
The ALL form of the disease most commonly occurs in younger children ages 2 to 8, but it can affect all age groups. AML can occur at any age, but it is somewhat more common before the age of 2 and during the teenage years.
Although experts don't know exactly what causes leukemia, it seems that some types of childhood leukemia may be linked to genetic or environmental factors.
Kids have a greater chance of developing ALL or AML if they have an identical twin who was diagnosed with the illness at a young age. (Nonidentical twins and other siblings of children with leukemia have a higher than average risk of developing this illness.) Also, children who have inherited certain genetic problems — such as Li-Fraumeni syndrome, Down syndrome, Klinefelter syndrome, neurofibromatosis, ataxia telangectasia, or Fanconi's anemia — have a higher risk of developing leukemia.
Children who have received prior radiation or chemotherapy for other types of cancer also have a higher risk for leukemia, as do kids who are receiving medical drugs to suppress their immune systems after organ transplants.
In most cases, neither parents nor kids have control over the factors that trigger leukemia. Most leukemias arise from noninherited mutations (changes) in the genes of growing blood cells. Because these errors occur randomly and unpredictably, there is currently no effective way to prevent most types of leukemia.
To limit the risk of prenatal radiation exposure as a trigger for leukemia (especially ALL), women who are pregnant or who suspect that they might be pregnant should always inform their doctors before undergoing tests or medical procedures that involve radiation (such as X-rays).
Because their infection-fighting white blood cells are defective, kids with leukemia may have more viral or bacterial infections than usual. They also may become anemic because leukemia affects the bone marrow's production of oxygen-carrying red blood cells. This makes them appear pale, and they may become abnormally tired and short of breath while playing.
Children with leukemia might bruise and bleed very easily, experience frequent nosebleeds, or bleed for an unusually long time after even a minor cut because leukemia destroys the bone marrow's ability to produce clot-forming platelets.
Other symptoms of leukemia can include:
- pain in the bones or joints, sometimes causing a limp
- swollen lymph nodes (sometimes called swollen glands) in the neck, groin, or elsewhere
- an abnormally tired feeling
- poor appetite
- fevers with no other symptoms
- abdominal pain (caused by abnormal blood cells building up in organs like the kidneys, liver, or spleen)
Occasionally, the spread of leukemia to the brain can cause headaches, seizures, balance problems, or abnormal vision. If ALL spreads to the lymph nodes inside the chest, the enlarged mass can crowd the trachea (windpipe) and important blood vessels, leading to breathing problems, and interfere with blood flow to and from the heart.
To determine whether a child has leukemia, a doctor will do a physical examination to check for signs of infection, anemia, abnormal bleeding, and swollen lymph nodes. The doctor will also feel the child's abdomen to check the liver and spleen because these organs can become enlarged by some childhood cancers.
The doctor also will take a medical history by asking about symptoms, past health, the family's health history, medications the child is taking, allergies, and other issues.
After this exam, the doctor will order a CBC (complete blood count) to measure the numbers of white cells, red cells, and platelets in the child's blood. A blood smear will be examined under a microscope to check for certain specific types of abnormal blood cells usually seen in patients with leukemia. Blood chemistries also will be checked.
Then, depending on the results of the physical exam and preliminary blood tests, the child might need:
- a bone marrow biopsy and aspiration, in which marrow samples are removed (usually from the back of the hip) for testing
- a lymph node biopsy, in which lymph nodes are removed and examined under a microscope to look for abnormal cells
- a lumbar puncture (spinal tap), where a sample of spinal fluid is removed from the lower back and examined for evidence of abnormal cells. This will show whether the leukemia has spread to the central nervous system (brain and spinal cord).
- imaging studies, such as X-rays, ultrasounds, CT scans, or MRIs
Besides these basic lab tests, cell evaluations might be done, including genetic studies to distinguish between specific types of leukemia and certain features of the leukemia cells. Kids will receive anesthesia or sedative medications for any painful procedures.
Regular checkups can spot early symptoms of leukemia in the relatively rare cases where this cancer is linked to an inherited genetic problem, to prior cancer treatment, or to the use of immunosuppressive drugs for organ transplants.
Kids who are diagnosed with leukemia are referred to a pediatric oncologist, a specialist in childhood cancer, for evaluation, treatment, and close monitoring.
Treatment for leukemia usually is carried out by a team of specialists, including nurses, social workers, psychologists, surgeons, and other health care professionals. Certain patient features (such as age and initial white blood cell count) are used to help doctors decide which type of treatment will provide the best chance for a cure.
Chemotherapy is the main treatment for childhood leukemia, although the dosages and drug combinations may differ. Chemo can be given by mouth, into a vein, or into the spinal fluid.
Intensive leukemia chemotherapy has certain side effects, including hair loss, nausea and vomiting, and increased risk for infection or bleeding in the short term, as well as other potential health problems later. As a child is treated for leukemia, the cancer treatment team will watch closely for those side effects and treat them as needed.
Other types of treatment include radiation therapy (high-energy rays that kill cancer cells), targeted therapy (specific drugs that identify and attack cancer cells without hurting normal cells), and stem cell transplants (the introduction of healthy stem cells into the body).
With the proper treatment, the outlook for kids and teens who are diagnosed with leukemia is quite good. Most childhood leukemias have very high remission rates, with some up to 90% (remission means there is no longer evidence of cancer cells in the body). Overall cure rates differ depending on the specific features of the disease. And the majority of kids can be cured of the disease (meaning that they are in permanent remission).