Neuroplastic Response following Radiotherapy for Pediatric Brain Tumors: A Pilot Study

Publication date: Available online 17 March 2016
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Carol L. Armstrong, Michael J. Fisher, Yimei Li, Robert A. Lustig, Jean B. Belasco, Jane E. Minturn, Christine E. Hill-Kayser, Sonny Batra, Peter C. Phillips
Purpose/ObjectivesClinically effective measurement of cognitive toxicity from photon radiotherapy (XRT) should be accurate, sensitive, and specific. This pilot study tests translational findings on phasic changes in children's memory systems that are sensitive and insensitive to toxic XRT effects, to identify a possible neuroplastic effect.Methods and MaterialsMemory processes were prospectively tested pre-XRT and at three later time points up to two years in 35 non-recurred children with mixed primary brain tumors. Memory processes were verbal-semantic, visual-semantic, and visual-perceptual, including accuracy, speed to recall, encoding, retrieval, and recognition. The mixed effects model included time (to estimate slope), covariates (age, tumor locus, XRT field, and medications) as fixed effects, and individual random intercepts. A sensitivity analysis examined the influence of XRT dose to the hippocampi on memory.ResultsRetrieval from long-term verbal-semantic memory declined two months after completing XRT, as seen in adults, and was lowest at one year, which was delayed in comparison to adults. Double dissociation from visual-perceptual memory at baseline and two months was found, consistent with adults. Recovery was demonstrated two years after XRT. Patterns were unchanged when dose to hippocampus was included in the model.ConclusionsVerbal and semantic long-term retrieval is specifically sensitive to XRT-related cognitive dysfunction, without effect on visual-perceptual memory. Children reached nadir in XRT-sensitive memory one year post-XRT, and recovered by two years, which is later than that observed in adults. The protracted period of post-XRT injury may represent the maturation of the human hippocampus and white matter into late adolescence.

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