paediatrics Brussels 17

559

Volume 90 Number 3 2014

Radiation effects in medulloblastoma

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Fig. 2. Iso-effect curves of age at the time of irradiation modeled according to the percentage of a specific brain region receiving a mean dose in excess of a specified amount. V25 Gy þ represents the percent volume of the brain receiving dose in excess of 25 Gy. TD 50/5 (tolerance dose for a given normal tissue that within 5 years will cause a maximal [unacceptable] 50% complication rate) for brain (a), left temporal lobe (b), and right temporal lobe (c).

decline in scores. Depending on the outcome measure, the decline exceeded 4 points per year in some cases. As anticipated, age had a significant impact on decline in all measures, and the rate of decline was inversely proportional to age at the time of irradiation. The most important information from this study was the association between radiation dose and cognitive test scores. Similar to our previous work, we were able to show regional differences in radiation dose and effect (13) . In this study we expanded the association between dose, volume, and outcome measures to include additional structures and aca- demic achievement. Increasing mean dose to all volumes except for the left hippocampus impacted IQ. Increasing mean dose to all volumes except the infratentorial brain and

8 years, < 30 Gy and 8 years, < 35 Gy and 10 years, and < 40 Gy and 12 years ( Fig. 2 a-c).

Discussion

Patients with MB treated with postoperative CSI and postirradiation chemotherapy experience a decline in cognitive test scores during the first 5 years after treatment, and a variety of clinical variables contributed to the base- line scores or decline. The presence of CSF shunt, sex, and race had the greatest impact on baseline IQ scores. High- risk classification, female sex, the presence of CSF shunt, and the extent of resection had a significant impact on