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Modeling radiation dosimetry to predict cognitive outcomes in pediatric patients with CNS embryonal tumors including medulloblastoma.

Merchant TE, Kiehna EN, Li C, Shukla H, Sengupta S, Xiong X, Gajjar A, Mulhern RK

Division of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.

PURPOSE: Model the effects of radiation dosimetry on IQ among pediatric patients with central nervous system (CNS) tumors. METHODS AND MATERIALS: Pediatric patients with CNS embryonal tumors (n = 39) were prospectively evaluated with serial cognitive testing, before and after treatment with postoperative, risk-adapted craniospinal irradiation (CSI) and conformal primary-site irradiation, followed by chemotherapy. Differential dose-volume data for 5 brain volumes (total brain, supratentorial brain, infratentorial brain, and left and right temporal lobes) were correlated with IQ after surgery and at follow-up by use of linear regression. RESULTS: When the dose distribution was partitioned into 2 levels, both had a significantly negative effect on longitudinal IQ across all 5 brain volumes. When the dose distribution was partitioned into 3 levels (low, medium, and high), exposure to the supratentorial brain appeared to have the most significant impact. For most models, each Gy of exposure had a similar effect on IQ decline, regardless of dose level. CONCLUSIONS: Our results suggest that radiation dosimetry data from 5 brain volumes can be used to predict decline in longitudinal IQ. Despite measures to reduce radiation dose and treatment volume, the volume that receives the highest dose continues to have the greatest effect, which supports current volume-reduction efforts.

Published 18 April 2006 in Int J Radiat Oncol Biol Phys, 65(1): 210-21.
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