Unlike cranial radiation, chemotherapy for children with a certain type of leukemia does not appear to have harmful long-term effects on intelligence, even at high doses, a new study shows.
Radiation to the brain had long been the standard treatment for acute lymphoblastic leukemia (ALL). While this approach is effective it can damage the brain, with particularly harmful effects in young children, Dr. Brenda J. Spiegler of the Hospital for Sick Children in Toronto and colleagues write in the Journal of Clinical Oncology.
Treatment targeting the central nervous system (that is, the brain and spinal cord) is essential for ALL patients, they add, and therapies other than radiation, such as intravenous methotrexate, are increasingly being used. But the effects of these therapies on neurocognitive development are not clear, Spiegler and her colleagues note.
To investigate, the researchers tested 79 patients diagnosed with ALL between the ages of one and five years for intelligence, academic achievement, attention and memory at an average of 10 years after their diagnosis. All had received the same basic chemotherapy regimen, while 25 also had cranial radiation therapy, 32 were treated with high-dose methotrexate in addition to standard chemo, and 22 received very high dose methotrexate.
Spiegler and her team found no difference in intelligence and memory scores between the two methotrexate groups. These patients scored close to the population average on 17 out of 18 measures of cognitive function. However, children who had received radiation to the brain scored worse than the chemo patients on most measures, and significantly lower than the population average.
The degree of decrease in the scores of the radiation group was important, the researchers report, "because children with generalized deficits of this order often require special accommodations to their academic programming."
Conversely, they conclude, treatment with methotrexate, even at very high doses, appears to be "relatively benign" in its effects on neurocognitive development and intelligence.
SOURCE: Journal of Clinical Oncology, August 20, 2006.
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