Full-scale IQ Drop Greater for Childhood Cancer Survivors Younger Than 15

Rakesh Jalali and colleagues studied the effect that varying radiation doses has on different volumes of normal structures in "Factors Influencing Neurocognitive Outcomes in Young Patients With Benign and Low-grade Brain Tumors Treated With Stereotactic Conformal Radiotherapy," available at http://www.redjournal.org.

The authors assessed the neurocognitive outcomes for pediatric and teenaged patients with residual or progressive brain tumors: 10 craniopharyngioma, eight cerebellar astrocytoma, six optic pathway glioma and four cerebral low-grade glioma. The study participants received a dose of 54 Gy in 30 fractions over 6 weeks and the researchers followed up with neuropsychological assessments during subsequent examinations following one at baseline prior to therapy. The change in IQ score was correlated to factors that included dose-volume to normal structures.

Although the average full-scale IQ did not drop, patients younger than 15 experienced had a significantly greater chance of having the FSIQ drop more than 10 percent (53% vs. 10%, p = 0.03). In turn, when the researchers compared dosimetric measures, the patients with a greater than 10 percent decline in IQ had received more than 43 Gy to more than 13 percent of the left temporal lobe.

"Although the overall mean full-scale IQ (FSIQ) at baseline before radiation therapy remained unchanged at two-year follow-up after SCRT, one-third of patients did show a greater than 10 percent decline in FSIQ as compared with baseline," noted the authors.

Radiation therapy to other normal structures such as the supratentorial brain, the right temporal lobe and frontal lobes did not reveal the same correlation, stated Jalali et al.

"Our prospectively collected dosimetric data show younger age and radiotherapy doses to left temporal lobe to be predictors of neurocognitive decline, and may well be used as possible dose constraints for high-precision radiotherapy planning," the authors concluded.