paediatrics Brussels 17

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Volume 90 Number 3 2014

Radiation effects in medulloblastoma

Effect of increasing mean dose on cognitive test scores by brain volume

Table 3

Estimated IQ

WIAT math

WIAT reading

WIAT spelling

Normal tissue volume

þ

þ

þ

þ

Entire brain

.0121 .0161 .0032 .0005 .0751 .0130 .0002

< .0001 < .0001 < .0001 < .0001 < .0001 < .0001 < .0001

.0096 .0251 .0184 .0053

.0007 .0009 .0013 .0009 .0025 .0016 .0034

n.s. n.s. n.s. n.s. n.s. n.s.

< .0001 < .0001 < .0001 < .0001 < .0001 < .0001 < .0001

n.s. n.s. n.s. n.s. n.s. n.s. n.s.

.0002 .0002 .0002

Supratentorial brain Temporal lobe (left) Temporal lobe (right) Hippocampus (left) Hippocampus (right) Infratentorial brain

.0184

< .0001

n.s. n.s. n.s.

.0001

< .0001

.0001

Abbreviation: n.s. Z not significant. Other abbreviations as in Table 2 . P values are grouped in columns according to the inclusion ( þ ) or exclusion ( ) of age in the model.

pts). Cerebrospinal fluid shunt: EIQ was higher at baseline (12.58 pts) in patients who did not have a CSF shunt ( P Z .0478), and those without CSF shunts had a lower rate of decline in math ( P Z .0025, 4.79 pts/y) and reading scores ( P Z .0319, 2.32 pts/y). Extent of resection: Baseline math scores were higher in patients who underwent < GTR ( P Z .0091, 9.97 pts). Gross total resection was associated with a slower rate of decline in reading scores ( P Z .0269, 2.25 pts/y) than in those who underwent < GTR. Age at RT: With the exception of math and reading scores, age (time of diagnosis or irradiation) had a highly significant impact on the rate of decline in all test scores (EIQ, P Z .0141; Math, P Z .1832; Reading, P Z .0688; Spelling, P Z .0424).

Impact of mean radiation dose on longitudinal trends in cognitive scores

The longitudinal trends in cognitive scores were modeled by time since irradiation and mean dose. Increasing mean dose to all volumes had a statistically significant negative impact on EIQ. Increasing mean dose to all normal tissue volumes except for the infratentorial brain and hippocampi had a statistically significant negative impact on math scores. Increasing mean dose to the right temporal lobe had a statistically significant negative impact on reading scores. The impact of increasing mean dose to the right hippo- campus was borderline significant. When age was included,

Estimated IQ

Math

70 60 50 40 30 20 10 0 70 60 50 40 30 20 10 0

70 60 50 40 30 20 10 0 70 60 50 40 30 20 10 0

Intratent Hippo L Hippo R Temporal L Temporal R Brain Supratent

Intratent Hippo L Hippo R

Temporal L Temporal R Brain Supratent

Dose (Gy) Dose (Gy)

Dose (Gy) Dose (Gy)

3 yrs 5 yrs 8 yrs 10 yrs 12 yrs 15 yrs

3 yrs 5 yrs 8 yrs 10 yrs 12 yrs 15 yrs

Reading

Spelling

Intratent Hippo L Hippo R

Intratent Hippo L Hippo R

Temporal L Temporal R Brain Supratent

Temporal L Temporal R Brain Supratent

3 yrs 5 yrs 8 yrs 10 yrs 12 yrs 15 yrs

3 yrs 5 yrs 8 yrs 10 yrs 12 yrs 15 yrs

Fig. 1. Estimated iso-effect curves of mean dose by brain volume and age at the time of irradiation representing a probability of below-average IQ or academic achievement 5 years after treatment. Each graph represents a different cognitive test, and each curve represents a different normal tissue volume. Missing estimates indicate that the model calculated a dose that was outside the range of dose used to generate the models. Brain Z entire brain volume; EIQ Z estimated intelligence quotient; Hippo L Z left hippocampus; Hippo R Z right hippocampus; Infratent Z infratentorial brain; Math Z Wechsler Individual Achievement Test (WIAT) math scores; Reading Z WIAT reading scores; Spelling Z WIAT spelling scores; Supratent Z supratentorial brain; Temporal L Z left temporal lobe; Temporal R Z right temporal lobe.