Acute lymphoblastic leukemia (ALL) is the most common form of childhood cancer, with more than 2,000 children in the United States diagnosed each year. Survival rates for ALL range from 70% to 85%, depending on risk factors. Patients considered to have high-risk ALL are those with a white blood cell count >50,000/μL at diagnosis, age younger than 1 year or older than 10 years, boys with testicular disease at diagnosis, or children who have received steroids for >48 hours prior to diagnosis. These patients receive more intensive therapy because of their high-risk status.

Leukemic blasts are exquisitely sensitive to steroid therapy. In fact, in German studies in the mid-1980s to early 1990s, children with ALL were treated with prednisone plus intrathecal methotrexate alone. A peripheral blast count of <1,000/μL was achieved in 90% of these children, illustrating how effective steroids are at reducing the peripheral blast count in acute leukemia. Because initial white blood cell count is an important prognostic indicator in pediatric ALL, steroid therapy for >48 hours prior to a diagnosis of ALL automatically places the child into a higher risk category. In some cases, these children are nonrandomly assigned to receive craniospinal irradiation, depending on the length of the steroid therapy. Craniospinal irradiation can cause learning disabilities and developmental delay in children younger than 5 years. This is extremely important, because ALL is most commonly diagnosed in children aged 2 to 4 years.