Prognostic importance of systemic clearance of methotrexate in childhood acute lymphoblastic leukemia

Pharmacokinetic studies of methotrexate have been carried out in 21 children with acute lymphoblastic leukemia diagnosed in 1981. Children were treated with intermediate dose (500 mg/m2) methotrexate in keeping with the 1981 ALL treatment Protocol of the Hungarian Childhood Leukemia Working Group. Of the 21 children, 8 relapsed, and 13 are in continuous complete remission. In the relapsed patients significantly increased systemic clearance of methotrexate was observed at the time of the second methotrexate treatment cycle compared with the calculated value after the first administration of the drug. No such change in the clearance was found in patients who are still in remission. There was no difference between children who relapsed or who are in remission in the elimination half-time of the drug. Age, sex, WBC at diagnosis, and systemic clearance of methotrexate were found to be connected with the probability of relapse in the patients studied. The possible reasons for the prognostic role of systemic methotrexate clearance are discussed.