Subtle white matter volume differences in children treated for medulloblastoma with conventional or reduced dose craniospinal irradiation

Medulloblastoma is the most common malignant brain tumor in children, and a pproximately seventy percent of average-risk patients will achieve long-ter m survival. Craniospinal irradiation (CSI), combined with chemotherapy and surgery, is currently the mainstay of treatment bur places children who sur vive at risk for serious neurocognitive sequelae. These sequelae are intens ified with a younger age at treatment, greater elapsed time following treat ment, and an increased radiation dose. Many newer treatment approaches have attempted to address this problem by reducing the dose of the CSI componen t of radiation therapy while maintaining the current survival rates. This s tudy evaluates longitudinal MR imaging during therapy to assess the impact of the two CSI doses (conventional [36 Gy] and reduced [23.4 Cy]) on normal appearing white matter volumes (NAWMV) evaluated in a single index slice. Twenty-six children and young adults at least three years of age enrolled o n an institutional protocol for newly diagnosed, previously untreated prima ry medulloblastoma. had at least four MR examinations over a minimum nine m onth period following CSI. These serial volumes were evaluated as a functio n of time since CSI in three analyses: 1) all subjects, 2) subjects stratif ied by age at CSI, and 3) subjects stratified by CSI dose. The first analys is demonstrated that medulloblastoma patients treated with CSI have a signi ficant loss of NAWMV in contradistiction to normally expected maturation. S tratifying the patients by age at CSI found no significant differences in t he rate of NAWMV loss. The final analysis stratified the patients by CSI do se and revealed that the rate of NAWMV loss was 23% slower in children rece iving reduced-dose. Serial quantitative MR measures of NAWMV may provide a neuroanatomical substrate for assessing functional impact of CSI on normal brain function following treatment for medulloblastoma. (C) 2000 Elsevier S cience Inc. All rights reserved.