Stages of Childhood Acute Lymphoblastic Leukemia

Once childhood ALL has been diagnosed, tests are done to find out if the cancer has spread to the central nervous system (brain and spinal cord), testicles, or to other parts of the body.

The extent or spread of cancer is usually described as stages. For childhood acute lymphoblastic leukemia (ALL), risk groups are used instead of stages. The following tests and procedures may be used to determine the risk group:

• Lumbar puncture: A procedure used to collect cerebrospinal fluid from the spinal column. This is done by placing a needle into the spinal column. This procedure is also called an LP or spinal tap.
• Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body. The chest x-ray is done to see if leukemiacells are forming a mass in the middle of the chest.
• Testicularbiopsy: The removal of cells or tissues from the testicles so they can be viewed under a microscope by a pathologist to check for signs of cancer. This procedure is done only if there seems to be anything unusual about the testicles during the physical exam.

There are three ways that cancer spreads in the body.

When cancer cells spread outside the blood, a solid tumor may form. This process is called metastasis. The three ways that cancer cells spread in the body are:

• Through the blood. Cancer cells travel through the blood, invade solid tissues in the body, such as the brain or heart, and form a solid tumor.
• Through the lymph system. Cancer cells invade the lymph system, travel through the lymph vessels, and form a solid tumor in other parts of the body.
• Through solid tissue. Cancer cells that have formed a solid tumor spread to tissues in the surrounding area.

The new (metastatic) tumor is the same type of cancer as the primary cancer. For example, if leukemia cells spread to the brain, the cancer cells in the brain are actually leukemia cells. The disease is metastatic leukemia, not brain cancer.

In childhood ALL, risk groups are used instead of stages.

Because ALL is a disease of the blood cells, it has already spread throughout the body at diagnosis. There is no staging system for ALL. Risk groups are used to plan treatment.

Risk groups are described as:

• Standard (low) risk: Includes children aged 1 to 9 years who have a white blood cell count of less than 50,000/µL at diagnosis.
• High risk: Includes children younger than 1 year or older than 9 years and children who have a white blood cell count of 50,000/µL or more at diagnosis.

Other factors that affect the risk group include the following:

• Whether the leukemia cells formed from B lymphocytes or T lymphocytes.
• Whether there are certain changes in the chromosomes of the lymphocytes.
• How quickly the leukemia responds to initial therapy.

It is important to know the risk group in order to plan treatment. Children with high risk ALL usually receive more aggressive treatment than children with standard risk ALL.