Purpose: To investigate the neuropsychologic effects of cranial irradiation (CRT), intrathecal methotrexate (IT-MTX), and systemic methotrexate (SYS-MTX) in a cohort of pediatric patients with cancer who had either received no, moderate, or high doses of these treatments alone or in various combinations.
Patient and methods: Data were collected on 120 pediatric cancer patients from a large variety of diagnostic groups. Patients completed a comprehensive neuropsychologic test battery designed to assess most areas of cognitive functioning. In analyzing cancer treatment effects, the following variables were statistically controlled: (1) age, (2) socioeconomic status (SES), (3) age at diagnosis, (4) months since both onset and cessation of CNS treatments, (5) time missed from schooling, and (6) presence/type of CNS cancer.
Results: CRT, largely in combination with IT-MTX, was significantly associated with deficits in several, primarily nondominant, hemispheric neuropsychologic functions, even after control and other treatment variables were addressed. This relationship was somewhat, but not highly, dose-dependent at CRT doses greater than approximately 18 Gy, at least over the first several years posttreatment. While there was statistically significant evidence for cognitive impairment, absence from school during treatment and age at diagnosis were more predictive of reading and spelling academic achievement than having received CRT. IT-MTX and SYS-MTX alone were not associated with significant degrees of neuropsychologic involvement.
Conclusion: CRT, especially when administered with IT-MTX, at currently used dosages was associated with significant neuropsychologic impairment in children. These impairments are most likely to be reflected in nonverbal intelligence, perceptual abilities, and susceptibility to distraction. IT-MTX and SYS-MTX did not result in a consistent pattern of cognitive deficit.