Results of treatment of high risk childhood acute lymphoblastic leukemia.

Sixteen children with high risk acute lymphoblastic leukemia (ALL) who had one or more of the following risk factors: white cell count over 50 X 10(9)/liter, mediastinal mass, age under 2 or over 10 years, extramedullary involvement, or T-cell markers, were treated by a new protocol. All attained complete remission and 11 are still in their continuous first remission for 6-53 months. High activity of adenosine deaminase (ADA) in the leukemic cells seems to be an independent risk factor, as in the high ADA level group, 4 out of 7 patients relapsed and died, while none of the 8 patients with low ADA levels relapsed or died.