Deterioration of intellect among children surviving leukemia: IQ test changes modify estimates of treatment toxicity

This study assessed the association of young age at treatment, cranial irradiation, and time since treatment with intellectual deterioration among 49 long-term survivors of childhood leukemia. Ss had been randomized to receive low-dose cranial radiation therapy or high-dose chemotherapy. Longitudinal assessments of intellect were conducted. No significant effects of treatment group or age at treatment were detected. A small but statistically significant decline in mean full-scale IQ was noted over time (M = -3.6). Reanalysis with IQ test version included as a covariate eliminated IQ declines found initially. Results suggest (a) that there has been reduced toxicity of these methods of treatment and (b) that the magnitude and direction of error introduced by changing tests may approximate the magnitude of adverse effects on IQ from treatment.