Histogram of each patient's average methotrexate clearance. (A) Unadjusted methotrexate clearance for the 655 COG patients receiving the 4-hour infusion (blue), and the 624 receiving the 24-hour infusion (red). (B) Methotrexate clearance in all COG patients (n = 1279), adjusted for age, sex, race, and treatment arm (residual from a linear regression model).