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Abstract
Leukemias are the most common malignant neoplasms in childhood, accounting for about 41% of all malignancies that occur in children younger than 15 years of age. Acute lymphoblastic leukemia (ALL) is the commonest, constituting nearly one third of childhood cancers. The prognosis for children with ALL has improved dramatically over the past four decades. The identification of clinical and biologic features that predict treatment outcome has permitted the design of risk-directed clinical trials in childhood ALL. These clinical trials in ALL aim to reduce acute and long-term side effects in patients with a favorable prognosis by avoiding unnecessarily toxic treatment, while improving outcome for patients with high-risk leukemia by intensifying therapy. Effective risk-based therapy produces complete clinical remissions in at least 95% of patients>