DataSheet_1_Review of MR-Guided Radiotherapy for Esophageal Cancer.docx

In this review, we outline the potential benefits and the future role of MRI and MR-guided radiotherapy (MRgRT) in the management of esophageal cancer. Although not currently used in most clinical practice settings, MRI is a useful non-invasive imaging modality that provides excellent soft tissue contrast and the ability to visualize cancer physiology. Chemoradiation therapy with or without surgery is essential for the management of locally advanced esophageal cancer. MRI can help stage esophageal cancer, delineate the gross tumor volume (GTV), and assess the response to chemoradiotherapy. Integrated MRgRT systems can help overcome the challenge of esophageal motion due to respiratory motion by using real-time imaging and tumor tracking with respiratory gating. With daily on-table MRI, shifts in tumor position and tumor regression can be taken into account for online-adaptation. The combination of accurate GTV visualization, respiratory gating, and online adaptive planning, allows for tighter treatment volumes and improved sparing of the surrounding normal organs. This could lead to a reduction in radiotherapy induced cardiac toxicity, pneumonitis and post-operative complications. Tumor physiology as seen on diffusion weighted imaging or dynamic contrast enhancement can help individualize treatments based on the response to chemoradiotherapy. Patients with a complete response on MRI can be considered for organ preservation while patients with no response can be offered an earlier resection. In patients with a partial response to chemoradiotherapy, areas of residual cancer can be targeted for dose escalation. The tighter and more accurate targeting enabled with MRgRT may enable hypofractionated treatment schedules.

本综述旨在阐述磁共振成像（MRI）与磁共振引导放疗（MRgRT）在食管癌管理中的潜在价值与未来应用前景。尽管目前多数临床实践场景尚未常规应用MRI，但其作为一种无创成像技术，可提供优异的软组织对比度，并能可视化肿瘤生理学特征。对于局部晚期食管癌的管理，同步放化疗联合或不联合手术治疗是核心诊疗手段。MRI可辅助食管癌分期、勾画大体肿瘤体积（GTV），并评估同步放化疗的疗效。一体化MRgRT系统可借助实时成像与呼吸门控肿瘤追踪技术，解决因呼吸运动导致的食管移位难题。通过每日术中MRI扫描，可实时掌握肿瘤位置变化与肿瘤退缩情况，从而开展在线自适应治疗。精准的GTV可视化、呼吸门控技术与在线自适应计划三者结合，可实现更精准的治疗靶区范围，并更好地保护周围正常组织器官。这有助于降低放疗诱导的心脏毒性、放射性肺炎及术后并发症发生率。通过弥散加权成像（Diffusion Weighted Imaging, DWI）或动态增强成像（Dynamic Contrast Enhancement, DCE）观察到的肿瘤生理学特征，可基于同步放化疗的疗效实现个体化治疗方案制定：MRI评估为完全缓解的患者可考虑实施器官保留治疗，疗效不佳者则可提前接受手术切除；对于同步放化疗后仅获得部分缓解的患者，可针对残留肿瘤区域进行剂量推注治疗。MRgRT所实现的更精准、更严格的靶区照射，可为开展大分割放疗方案提供可能。