Association of delivered drug dose and outcome for children with acute lymphoblastic leukemia and unfavorable presenting features.

Dose and dose intensity are believed critical for attaining a maximal therapeutic effect in drug-responsive tumor systems. Childhood acute lymphoblastic leukemia may be an example of such a drug-responsive system as it is cured with current chemotherapy in a majority of cases. Between August 1981 and May 1983, the Childrens Cancer Study Group enrolled 209 children with ALL and unfavorable presenting features in CCG-193P, a trial based on the Berlin Frankfurt Munster 76/79 regimen. The cumulative delivered dose of each medication was recorded prospectively. Patients who completed the intensive portion of therapy in continuous complete remission were ranked by the percentage of protocol required drug delivered from the initiation of therapy to that date. No association was found between delivery of any single drug and subsequent disease-free survival. However, when patients were ranked by the sum of the percentages of protocol vincristine, l-asparaginase, and anthracycline delivered, children in the approximate middle and lower tertiles were 3 and 5 times more likely to have had a subsequent relapse than were those in the upper tertile (P = 0.025, test for trend). Delivery of the full protocol prescribed dose of these agents may have been critical, but corroboration is certainly needed. Only prospective trials can determine if children with acute lymphoblastic leukemia and unfavorable presenting features might benefit from greater use of vincristine, l-asparaginase, and/or anthracycline.