paediatrics Brussels 17

550

Merchant et al.

International Journal of Radiation Oncology Biology Physics

posterior cerebellum (50.6 5.82 Gy) were calculated. Baseline mean neurocognitive scores were within the normal range (mean SE) for WIAT reading (103.60 1.53), WIAT math (98.62 1.93), WIAT spelling (102.30 2.21), VAL (94.66 2.54), and IQ, which was below average (96.59 1.78). Based on longitudinal ob- servations through the first 5 years after irradiation, improvement was observed in IQ and VAL scores at the rate of 0.1803 0.246 points/year ( P Z .467) and 1.361 0.371 points/year ( P .001), respectively. Among the academic achievement scores, WIAT math scores remained unchanged over time, whereas a modest but sta- tistically significant decline was observed in WIAT reading scores at the rate of 0.96 0.24 points/year ( P .001) and in WIAT spelling scores of 0.85 0.35 points/year ( P Z .019) ( Table 1 ). The association between clinical variables and baseline cognitive scores was investigated. There was a negative correlation between baseline scores and the presence of a CSF shunt for all of the cognitive measures. This correla- tion was statistically significant for IQ ( 11.55, P Z .002), WIAT reading ( 8.17, P Z .003), WIAT math ( 7.15, P Z .036), WIAT spelling ( 6.08, P Z .057), and VAL ( 9.05, P .037). There was a positive correlation with age at the time of irradiation and baseline IQ scores (1.31 pa- tients/1 year-age-difference [yad]; ie, difference between the age of the individual patient and group mean; P Z .006) and VAL scores (2.24 patients/yad, P .001) and negative correlation between age and baseline WIAT reading scores ( 0.91 patients/yad, P .001). The use of preirradiation chemotherapy had no impact on baseline scores. None of the clinical variables of age at irradiation, CSF shunt, or preirradiation chemotherapy impacted longitudinal change in neurocognitive scores.

significant association between IQ scores and infratentorial, anterior cerebellar, and posterior cerebellar mean doses and time after treatment. The magnitude of the effect ranged from 0.150 patients/Gy/year for the posterior cerebellum to 0.190 patients/Gy/year for the infratentorial brain.

Effect of cerebellar dosimetry on longitudinal WIAT reading, math, and spelling scores

When WIAT Reading, Math, and Spelling scores were estimated individually by using mixed model equations, adjusted for time since irradiation, infratentorial and pos- terior cerebellar mean doses were found to have signifi- cantly negative effects on the longitudinal trend of all WIAT academic scores, ranging from 0.111 patients/Gy/ year for the posterior cerebellum on WIAT reading scores to 0.164 patients/Gy/year for the infratentorial brain on WIAT math scores ( Table 2 ). There was an association between the gross tumor volume and longitudinal VAL scores. The magnitude of the effect was 0.0729 patients/mL/year ( P Z .0222). There was no association between number of surgery procedures or pre- irradiation extent of resection and longitudinal scores. Fifty-one patients had 1 surgery, 21 patients had 2 opera- tions, and 4 patients underwent 4 attempts at resection prior to irradiation. The preoperative extent of resection was gross-total resection (GTR) in 61, near total resection (NTR) in 11 and subtotal resection (STR) in 4. There was an association between mean dose to the left hippocampus and longitudinal IQ ( 0.0558 patients/Gy/year; P Z .0305) and VAL ( 0.0517 patients/Gy/year; P Z .0063) scores. There was an association between mean dose to the right hippocampus and VAL ( 0.0683 patients/Gy/year; P Z .0024) scores. There was no association between cu- mulative total dose (54 Gy vs 59.4 Gy) and longitudinal cognitive scores. Eight patients received 54 Gy, and the remainder received 59.4 Gy. Effect of tumor volume, surgery, and RT parameters

Effect of cerebellar dosimetry on longitudinal IQ scores

When IQ scores were estimated using a mixed model equation adjusted for time since irradiation, there was a

Table 1 Baseline and longitudinal trends in cognitive tests scores in 76 children with infratentorial ependymoma treated with postoperative irradiation

Slope y

Baseline (intercept) *

Estimate

SE

P

Estimate

SE

P

Cognitive test

No. of evaluations

IQ

559 363 365 361 292

96.5869

1.7809 1.5313 1.9306 2.2108 2.5354

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

0.1803 0.9639 0.3460 0.8536 1.3610

0.2460 0.2458 0.3249 0.3463

.4671 .0004 .2918 .0190 .0009

WIAT reading WIAT math WIAT spelling

103.60

98.6237

102.30

VAL

94.6609

0.370

Abbreviations: IQ Z intelligence quotient; VAL Z visual-auditory learning; WIAT Z Wechsler Individual Achievement Test. * Intercept scores represent neurocognitive scores at conformal radiation therapy baseline. Scores are reported as standard scores, which have a normative mean of 100 and a standard deviation of 15. y Slope represents change in neurocognitive scores in standard points per year.