Higher RT Dose in Pediatric Brain Tumors Limited Vocabulary Development

A small study has found that among children with primary brain tumors who were treated with cranial radiation, cerebral volume and radiation dose may affect the rate of vocabulary development. The results of the study were published in Cancer.

“Although the treatment of primary brain tumors in children, and medulloblastoma in particular, is associated with neurocognitive deficits, the underlying pathophysiology is unknown,” wrote Harold Agbahiwe, MD, of Johns Hopkins University School of Medicine in Baltimore, and colleagues. “We found a significant relation between cerebral volume and performance on the PPVT-3 (an IQ estimate), with larger volumes associated with higher scores.”

Cranial radiation is required in most children with primary brain tumors in order to achieve long-term disease control. Use of cranial radiation is associated with cognitive impairments later in life. As survival from primary brain tumors has improved, researchers have shifted their focus to improving long-term consequences of these diseases.

This prospective study was designed to look at the possible effects of radiation on cerebral, frontal lobe, and temporal lobe volumes and their associations with higher cognitive functioning. The researchers looked at 10 pediatric patients with primary brain tumors treated with cranial radiation therapy and compared them with 14 healthy children. They conducted neuropsychological assessments of language, memory, auditory and visual processing, and vocabulary at baseline, and 6, 15, and 27 months after radiation treatment.

Both study patients and control patients had significant increases in cerebral volume over time, but overall growth was higher in control patients. In addition, those patients with a higher cerebral volume were found to have significantly better performance on the vocabulary test (P = .05).

“Because cerebral volume increased with age and time in all children (both patients and controls), these results suggest that the reduced growth rate of cerebral volumes in patients was associated with slower vocabulary development,” the researchers wrote.

The researchers also found that higher radiation doses were associated with lower vocabulary scores in patients, suggesting that “radiation dose affects performance on vocabulary measures in a dose-dependent manner.”

Finally, bilateral frontal and left temporal lobe volumes increased with age in all of the children in the study.

“Interestingly, the right frontal and right temporal lobe volumes differed significantly between patients and controls, and this persisted over time, with controls having higher volumes than patients,” the researchers wrote. “However, the neuropsychological tests associated with these lobar regions, Bead Memory and Visual Perception, respectively, did not differ between patients and controls.”

The researchers acknowledged that the small study size limits the study results.