为了研究新辅助化疗后弥漫加权磁共振成像（DW-MRI）作为预测性成像标志物在患有横纹肌肉瘤的患者中的可行性，我们进行了一项多中心回顾性研究，包括患有横纹肌肉瘤的儿童、青少年和年轻成人患者，国际肌肉瘤研究组III/IV，在根据欧洲儿童软组织肉瘤研究小组（EpSSG）RMS2005或MTS2008研究进行治疗。DW-MRI按照医院的规定进行。我们进行了二维单层肿瘤描绘。进行初步分析时，剔除了坏死或出血区域。提取了平均值、中位数和第5和第95个表观扩散系数（ADC）。 在包括134名患者的研究中，82名患者在诊断和反应以及DW-MRI扫描中具有可测量的肿瘤和足够质量的图像被纳入分析。观察到扫描获取协议和扫描仪的技术异质性。诊断时的平均ADC为1.1（95％置信区间[CI]：1.1-1.2）（所有ADC以* 10-3 mm2/s表示），而反应评估时为1.6（1.5-1.6）。诊断时的第5百分位ADC为0.8（0.7-0.9），反应时为1.1（1.0-1.2）。新辅助化疗后的平均ADC绝对变化为0.4（0.3-0.5）。对ADC与临床参数的探索性分析显示，在泡状和胚胎性组织学之间，诊断时的平均ADC存在显著差异。在诊断后九周的里程碑分析显示，平均ADC变化与无事件生存之间无显著关联（风险比为1.3 [0.6-3.2]）。 观察到化疗后第5百分位ADC和平均ADC发生了显著变化。在中心之间以及患者个体中，DW-MRI采集协议存在显著的异质性。 ©2023. 作者。

To investigate the feasibility of diffusion-weighted magnetic resonance imaging (DW-MRI) as a predictive imaging marker after neoadjuvant chemotherapy in patients with rhabdomyosarcoma.We performed a multicenter retrospective study including pediatric, adolescent and young adult patients with rhabdomyosarcoma, Intergroup Rhabdomyosarcoma Study group III/IV, treated according to the European paediatric Soft tissue sarcoma Study Group (EpSSG) RMS2005 or MTS2008 studies. DW-MRI was performed according to institutional protocols. We performed two-dimensional single-slice tumor delineation. Areas of necrosis or hemorrhage were delineated to be excluded in the primary analysis. Mean, median and 5th and 95th apparent diffusion coefficient (ADC) were extracted.Of 134 included patients, 82 had measurable tumor at diagnosis and response and DW-MRI scans of adequate quality and were included in the analysis. Technical heterogeneity in scan acquisition protocols and scanners was observed. Mean ADC at diagnosis was 1.1 (95% confidence interval [CI]: 1.1-1.2) (all ADC expressed in * 10-3 mm2/s), versus 1.6 (1.5-1.6) at response assessment. The 5th percentile ADC was 0.8 (0.7-0.9) at diagnosis and 1.1 (1.0-1.2) at response. Absolute change in mean ADC after neoadjuvant chemotherapy was 0.4 (0.3-0.5). Exploratory analyses for association between ADC and clinical parameters showed a significant difference in mean ADC at diagnosis for alveolar versus embryonal histology. Landmark analysis at nine weeks after the date of diagnosis showed no significant association (hazard ratio 1.3 [0.6-3.2]) between the mean ADC change and event-free survival.A significant change in the 5th percentile and the mean ADC after chemotherapy was observed. Strong heterogeneity was identified in DW-MRI acquisition protocols between centers and in individual patients.© 2023. The Author(s).