The currently accepted philosophy behind treatment of pediatric ALL is based on the recognition of the heterogeneity of the disease. Although it is no longer acceptable to treat all cases of childhood ALL with a single treatment regimen, there are 4 basic phases in all treatment protocols. These phases include remission induction, treatment of clinical or occult CNS disease (consolidation), intensification, and maintenance therapy. The goals of induction therapy are to attain remission, defined as the absence of evidence of leukemia, which includes the absence of CNS or testicular disease, and to have bone marrow examination showing normal cellularity with fewer than 5% lymphoblasts. The 3-drug combination of vincristine, a glucocorticoid, and L-asparaginase successfully induces remission in 95% of children with ALL.
Intrathecal therapy has increased event-free survival by preventing relapse in the CNS where the blood-brain barrier provides a "sanctuary" from systemic chemotherapeutic agents.[22,23] Although cranial irradiation is used in some protocols, it is usually restricted to therapy for high-risk ALL and patients with proven CNS disease because of the significant neurotoxic sequelae. Given immediately after remission induction, consolidation therapy is particularly important in high-risk ALL, such as T-cell ALL and the infant form of ALL, in addition to patients with CNS disease. Maintenance chemotherapy usually includes daily administration of 6-mercaptopurine (6MP) in addition to intermittent methotrexate. Duration of therapy differs among centers and protocols, but, on average, therapy lasts 2.5 years. Generally, boys are treated for 3 years and girls 2 years, secondary to the recognition that boys are more likely to relapse. Most relapses are treated with intensified regimens of chemotherapy.
Because of the relatively high rates of disease-free survival in ALL, hematopoietic stem cell transplantation is reserved for patients who fail to respond to induction therapy, those who relapse during treatment, or those who relapse within 1 year following completion of chemotherapy. Risk stratification has classically been based on the 2 prognostic factors that have been most consistent in retrospective analyses: age at presentation and initial WBC count. The future of ALL therapy involves gene-expression profiling and immunophenotyping to classify children into various risk groups that will influence treatment decisions. Although there is a growing consensus that this is feasible, it is not currently the standard of care.[25,26]
© 2005 Medscape
Cite this: Topics in Pediatric Leukemia -- Acute Lymphoblastic Leukemia - Medscape - Feb 28, 2005.