than 50,000 require more aggressive treatment. • type of leukemia—There are different kinds of childhood leukemia; pre-B-cell ALL is the most common and T-cell ALL is less common. • central nervous system disease—Children with leukemia in their spinal fluid at diagnosis require more aggressive treatment. • disease outside the bone marrow—Sometimes leukemia cells are seen in different parts of the body (such as the testicles). If your child is found to have disease in other parts of the body (called extramedul- lary disease ), the treatment needs to be more aggressive. • results of cytogenetics and FISH—Leukemia cells can carry certain genetic markers or abnormalities. These markers can affect the type of treatment your child receives. Some types of ALL (such as Philadel- phia chromosome ALL [also called BCR-ABL] or mixed lineage leukemia [MLL] gene rearrangement) can be more difficult to treat and require more aggressive therapy. If there are more chromosomes, called hyperdiploid , less aggressive chemotherapy may be needed. • treatment with steroids—Children who receive treatment with steroids before learning that they have leukemia may be placed in a higher-risk group. • response to treatment—A bone marrow test or a blood test, called minimal residual disease (MRD) , will be done on specific days during the first month of treatment. MRD is a test done on bone marrow or blood that determines if microscopic leukemia remains. It can show the prescense of leukemia down to 0.01%. If the MRD is high, more aggressive treatment will be needed. Typically these tests are done after 1. Low Risk Children between the age of 1 and 9.99 years old with a WBC count lower than 50,000 at diagnosis and all of these criteria: • no testicular disease • no leukemia in their spinal fluid at diagnosis • have “good or favorable” chromosome alterations in leukemia cells (these are called ETV6/RUNX1 fusion or trisomy 4,10) • do not have Down syndrome • did not receive steroids before diagnosis • MRD less than 0.01% after first week of chemotherapy and at the end of the first month of chemotherapy. 2. Average or Standard Risk Children younger than 1 year and 10 years or older with a WBC count lower than 50,000 at diagnosis and all of these criteria: • no testicular disease • very little leukemia in their spinal fluid at diagnosis (called CNS-2) • have “good or favorable” chromosome alterations in leukemia (ETV6/RUNX1 fusion or trisomy 4,10) • do not have Down syndrome • did not receive steroids before diagnosis • MRD in the first week of treatment of 0.01% or more, and MRD at the end of the first month of treatment of LESS than 0.01%. 1 week of chemotherapy and at the end of the first month of treatment. After the first month of therapy, each child is placed in one of four risk groups.
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