Factors associated with IQ scores in long-term survivors of childhood acute lymphoblastic leukemia

To identify factors which might be associated with intellectual function following treatment for childhood acute lymphoblastic leukemia, 50 long-term survivors were studied using the Wechsler Intelligence Scale for Children-Revised. All patients were diagnosed between 1972 and 1974 and were treated on a single clinical trial protocol with identical induction and maintenance chemotherapy plus central nervous system prophylaxis that included cranial radiation. The mean full scale IQ score for the group was 95 (SEM 2.0), with mean verbal IQ of 94.4 and mean performance IQ of 96.9. Factors which were found to be closely associated with a lower IQ score included female sex (in both verbal IQ and full-scale IQ), longer duration of chemotherapy (in performance IQ), and younger age at the time of radiation (in both verbal IQ and full-scale IQ). The age at the time of radiation was found to be significantly correlated with discrepancy between verbal and performance IQ, with younger age being associated with verbal IQ scores higher than performance IQ scores. When analyses were performed within specific subgroups of patients defined by sex and age at the time of radiation, dose of cranial radiation, concomitant intrathecal methotrexate therapy, and duration of therapy were all found to be correlated with a lower level of intellectual function. These preliminary findings provide direction for future studies to help identify high-risk patients.