Reddick W E, Russell J M, Glass J O, Xiong X, Mulhern R K, Langston J W, Merchant T E, Kun L E, Gajjar A
Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, USA.
Magn Reson Imaging. 2000 Sep;18(7):787-93. doi: 10.1016/s0730-725x(00)00182-x.
Medulloblastoma is the most common malignant brain tumor in children, and approximately seventy percent of average-risk patients will achieve long-term survival. Craniospinal irradiation (CSI), combined with chemotherapy and surgery, is currently the mainstay of treatment but places children who survive at risk for serious neurocognitive sequelae. These sequelae are intensified with a younger age at treatment, greater elapsed time following treatment, and an increased radiation dose. Many newer treatment approaches have attempted to address this problem by reducing the dose of the CSI component of radiation therapy while maintaining the current survival rates. This study evaluates longitudinal MR imaging during therapy to assess the impact of the two CSI doses (conventional [36 Gy] and reduced [23.4 Gy]) 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 on an institutional protocol for newly diagnosed, previously untreated primary medulloblastoma had at least four MR examinations over a minimum nine month period following CSI. These serial volumes were evaluated as a function of time since CSI in three analyses: 1) all subjects, 2) subjects stratified by age at CSI, and 3) subjects stratified by CSI dose. The first analysis demonstrated that medulloblastoma patients treated with CSI have a significant loss of NAWMV in contradistiction to normally expected maturation. Stratifying the patients by age at CSI found no significant differences in the rate of NAWMV loss. The final analysis stratified the patients by CSI dose and revealed that the rate of NAWMV loss was 23% slower in children receiving 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.
髓母细胞瘤是儿童最常见的恶性脑肿瘤，约70%的低风险患者可实现长期生存。颅脊髓照射（CSI）联合化疗和手术是目前的主要治疗方法，但存活下来的儿童有发生严重神经认知后遗症的风险。治疗时年龄越小、治疗后经过的时间越长以及辐射剂量增加，这些后遗症就会越严重。许多新的治疗方法试图通过降低放射治疗中CSI部分的剂量来解决这个问题，同时保持目前的生存率。本研究评估治疗期间的纵向磁共振成像，以评估两种CSI剂量（传统剂量[36 Gy]和降低剂量[23.4 Gy]）对在单个索引切片中评估的正常外观白质体积（NAWMV）的影响。26名至少三岁的儿童和年轻成人参加了一项机构方案，该方案针对新诊断的、未经治疗的原发性髓母细胞瘤，在CSI后的至少九个月内进行了至少四次磁共振检查。这些连续体积在三种分析中作为自CSI以来时间的函数进行评估：1）所有受试者，2）按CSI时年龄分层的受试者，3）按CSI剂量分层的受试者。第一项分析表明，接受CSI治疗的髓母细胞瘤患者的NAWMV显著减少，这与正常预期的成熟情况相反。按CSI时年龄对患者进行分层，发现NAWMV减少率没有显著差异。最后一项分析按CSI剂量对患者进行分层，结果显示接受低剂量治疗的儿童NAWMV减少率慢23%。NAWMV的系列定量磁共振测量可能为评估CSI对髓母细胞瘤治疗后正常脑功能的功能影响提供神经解剖学基础。
