The overall goal of this study is to see if we can increase the cure rate of high risk acute lymphoblastic leukemia (ALL) without increasing the side effects of therapy. Side effects are unintended and unwanted results of treatment.

The rate of survival continues to improve for children and adolescents with high risk ALL. However, leukemia in the central nervous system (CNS) (brain and spinal cord) has become an increasing cause of treatment failure. This study will use an established chemotherapy regimen that has been very effective for treating children and adolescents with high risk ALL and will test whether two different changes to the treatment can cure more patients.