Most types of cancer are classified by a process known as staging. Staging assigns numbered stages to cancers based on tumor size and how far the cancer spreads from the original site. Leukemia, however, is not staged because it involves all the bone marrow in the body and in many cases also spreads to other organs. For cases of acute lymphocytic leukemia (ALL) in children, risk groups are used instead of stages.

Certain prognostic factors have been identified to help a physician determine if a child requires more or less treatment. Based on these factors, the child is placed in a certain risk group. Treatment for the child depends on the risk group. These groups are:

• Low-risk
• Standard-risk
• High-risk
• Very-high risk

Prognostic factors for children with ALL include:

• Age at diagnosis. Children between the ages of 1 and 9 generally do better, while children younger than 1 or older than 10 are considered high-risk.
  
  
• White blood cell count. Children who have a white blood cell count greater than 50,000 cells per cubic millimeter at the time of diagnosis are classified as high-risk and are usually subjected to more intensive treatment.
  
  
• Gender. Girls with ALL have a slightly higher cure rate than boys.
  
  
• Race. African American and Hispanic children with ALL typically have a lower chance of being cured than children of other races.
  
  
• Organ spread. In boys with ALL, spread of the disease to the spinal fluid or the testicles increases the risk of a poor outcome.
  
  
• Immunophenotype of the leukemia cells. Immunophenotyping determines whether the cancer cells began from B-cells or T-cells. Children with early pre-B-cell or pre-B-cell ALL have a higher cure rate than those with T-cell or mature B-cell leukemia (Burkitt leukemia).
  
  
• Number of chromosomes. Children whose cancer cells have an increased number of chromosomes (hyperdiploidy) have a higher cure rate. Often, hyperdiploidy is expressed as a “DNA index” of more than 1.16. Likelihood of being cured is especially high when there is an extra chromosome 4 or 10. Children whose cancer cells have fewer cells than normal (hypodiploidy) have a lower cure rate.
  
  
• Translocations. A translocation is the transfer of DNA from one chromosome to another. Children whose cancer cells have a translocation between chromosomes 12 and 21 have a higher cure rate. Those with a translocation between chromosomes 9 and 22 (the Philadelphia chromosome), 1 and 19, or 4 and 11 have a lower cure rate.
  
  
• Response to chemotherapy. Children whose ALL responds completely to chemotherapy within one to two weeks of treatment have a better prognosis than those who do not respond as well.

Age at diagnosis and white blood cell count at diagnosis are considered the two most important prognostic factors in determining a child’s risk level.

Other factors that influence prognosis and treatment choices include:

• How quickly and how low the child’s white blood cell count falls after the initial treatment.
  
  
• Whether there are specific changes in the chromosomes of the lymphocytes.
  
  
• Whether the ALL has spread to the brain and spinal cord.

According to the American Cancer Society (ACS), the cure rate for the various risk levels of ALL in children includes: