Cognitive function in children with leukemia. Effect of radiation dose and time since irradiation.

The effect of two cranial radiation (CRTX) doses and the time since radiation therapy on cognitive functioning were studied in 35 children who completed therapy for acute lymphoblastic leukemia (ALL). The patients were grouped according to CRTX dose (2400 or 1800 cGy) and evaluated for general intelligence, academic achievement, and visual motor integration. Those who received 2400 cGy (n = 20) scored ten points below those treated with 1800 cGy (n = 15) on verbal intelligence quotient and achievement tests of reading, spelling, and arithmetic. The effect of time since radiation therapy on these measures of cognitive function was significant (P = 0.001 to 0.03); the effect of CRTX dose was not. Visual motor integration scores in both groups fell below the 33rd percentile. The effect of CRTX dose and time since radiation therapy on visual motor integration and performance intelligence quotient were not significant. Thus, the interval between treatment and the emergence of cognitive impairments may be longer after lower CRTX doses, and deficits in nonverbal areas such as visual motor integration may appear first. A larger study is needed to confirm these findings from a limited sample of long-term survivors of ALL.