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Full Scale IQ (FSIQ) changes in children treated with whole brain and partial brain irradiation. A review and
1Department of Radiation Oncology, University of Heidelberg, Heidelberg, Germany. mfuss@saci.org
Insights
Pediatric radiation therapy can impact intellectual function. Whole brain irradiation at doses over 24 Gy risks Full Scale IQ decline in children, especially younger ones. Partial brain irradiation is less damaging.
Area of Science:
- Pediatric Oncology
- Radiation Oncology
- Neuropsychology
Background:
- Neuropsychological impairment is a known risk following pediatric irradiation.
- Understanding the relationship between radiation dose, volume, age, and cognitive outcomes is crucial.
Purpose of the Study:
- To assess current knowledge on the impact of radiation dose and volume on neurocognitive outcomes in children.
- To analyze the correlation between radiation therapy parameters and Full Scale IQ (FSIQ) in pediatric patients.
Main Methods:
- A meta-analysis of 36 publications involving 1,938 children.
- Analysis of Full Scale IQ (FSIQ) data in relation to radiation dose, irradiated volume, and patient age.
Main Results:
- Whole brain irradiation shows a non-linear FSIQ decline with increasing dose, age-dependently.
- FSIQ decline is more pronounced in younger children (<3 years) at doses >24 Gy.
- Partial brain irradiation demonstrates minor FSIQ decline, with effects noted above 50 Gy.
Conclusions:
- Doses of 18-24 Gy whole brain irradiation may not significantly impact FSIQ in children >6 years old.
- Doses >24 Gy pose a substantial risk for FSIQ decline in all pediatric age groups.
- Partial brain irradiation is associated with less neurocognitive damage than whole brain irradiation at equivalent doses.
Purpose:
Neuropsychological impairment has been reported following whole brain and partial brain irradiation in children. The purpose of this analysis was to assess current knowledge, with focus on correlation with radiation dose, irradiated volume and age.
Method:
Full Scale IQ (FSIQ) data, representing 1,938 children, were derived from 36 publications and analyzed as to radiation dose, irradiated volume, and age.
Results:
FSIQ after whole brain irradiation showed a non-linear decline as dosage increased. The dose-effect relationship was age-related, with more pronounced FSIQ decline at younger age. FSIQ test results below the normal level (< 85) were found at doses higher than 24 and 36 Gy in children under age 3, and older than age 6, respectively. Mean FSIQ test result after 18 Gy was 100, thus at the mean standard value; a minor decline was detectable only when compared to test results of a control group. Young children scored at this dose in the low normal range. Partial brain irradiation caused minor FSIQ decline, with measurable effects at dose levels > 50 Gy.
Conclusion:
The collected data suggest that whole brain irradiation doses of 18 and 24 Gy have no major impact on intellectual outcome in children older than age 6, but may cause impairment in younger children. Doses > 24 Gy comprise a substantial risk for FSIQ decline, even in older children. At equal dose levels, partial brain irradiation is less damaging than whole brain irradiation. The authors are well aware of limitations in the interpretation of data collected for the current review. Thus, further research is required to evaluate the effect of low-dose whole brain irradiation as well as partial brain irradiation on FSIQ development.