磁共振成像在新辅助治疗后直肠癌再分期及疗效评估中的应用

Application of magnetic resonance imaging in TN restaging and efficacy evaluation after neoadjuvant therapyfor rectal cancer

新辅助放化疗联合全直肠系膜切除术（TME）已成为目前局部进展期直肠癌（cT3或cN＋）的标准治疗策略。新辅助放化疗后．术前TN再分期及疗效评估直接关系到下一步治疗方案的制定及预后判断．再分期及疗效评估成为临床医生普遍关注的问题．磁共振成像（MRI）是目前公认的直肠癌TN分期及疗效评估较为有效的评估手段之一，特别是功能磁共振在分子微观水平的反映，扩散加权成像（DWI）可以反映肿瘤细胞外水分子运动情况；多期动态对比增强磁共振成像（DCE-MRI）可从病理生理学角度间接反映肿瘤血管壁的通透性及肿瘤局部血流灌注情况。由于放疗后的水肿、炎性反应及纤维组织增生的影响．新辅助治疗后MRI对TN再分期的精确度以及MRI对疗效预测的准确性臼益受到国内外学者的关注。本文从新辅助治疗后再分期及局部疗效评估两个方面．对MRI的应用价值及局限性做一阐述。

Neoadjuvant chemoradiotherapy （NCRT） combined with total mesorectal excision （TME） has becomethe recommended standard treatment strategy for local advanced rectal cancer （cT3 or cN ＋ ）. After neoadjuvant chemoradiotherapy, preoperative T/N re-staging and efficacy evaluation of rectal cancer are directly related to the available treatment options and prognosis, so they are the common questions concerned by physicians. At present, magnetic resonance imaging （MRI） is acknowledged to be one of the more effective and feasible methods of T/N re-staging and efficacy evaluation, especially in the molecular microscopic scale. The diffusion weighted imaging （DWI） can reflect the movement of water molecules outside the tumor cells, and the multi-phase dynamic contrast enhanced MRI （DCE-MRI） can indirectly reflect the permeability of tumor vascular wall and local blood perfusion of tumor from the view of pathophysiological point. Because of the influence of edema, inflammatory response and fibrous tissue proliferation after radiotherapy, scholars both at home and abroad increasingly pay more attentions to the accuracy of T/N re-staging and efficacy prediction in MRI following neoadjuvant therapy. In this review, we elucidate the application value and limitation of MRI based on T/N re-staging and local efficacy evaluation.