High risk lymphoblastic leukemia in children: prognostic factors and management.

Most of the presenting clinical and biological features that have prognostic significance in childhood acute lymphoblastic leukemia are closely related, although they are not equally important. The predictive value of these factors can vary with the efficacy of the therapy delivered. Although there are no uniform criteria to define a high-risk group, an initially high leukocyte count and an age less than 1 or greater than 10 years at diagnosis are universally accepted as the most powerful indicators of a poor outcome. With advances in immunology and genetics, blast cell immunophenotypes and karyotypic abnormalities have emerged as independently significant prognostic factors. With this information, therapy can be tailored for patients at various risks of treatment failure. Using early aggressive therapy, more than 60% of patients are expected to be long-term survivors, but better therapy is still needed for those at high risk of relapse. Innovative approaches, such as bone marrow transplantation, phenotype-specific treatment, or pharmacokinetic-directed therapy, are being tested.