局部进展期直肠癌新辅助放化疗效果判断中MRI的应用价值

Value of magnetic resonance imaging in assessing the efficacy of neoadjuvant chemoradiotherapy for locally advanced rectal cancer

新辅助放化疗前后，对于局部进展期直肠癌进行全面和准确地评价，关系到治疗决策的选择，其中影像诊断是关键环节。解剖及功能MRI，已经被应用于局部进展期直肠癌新辅助放化疗效果的临床预判和评价。新辅助放化疗前，肿瘤下缘距肛缘小于或等于5 cm和直肠腔外血管侵犯，是预判新辅助放化疗效果的独立性因素。新辅助放化疗后，MRI肿瘤退缩程度分级（mrTRG）是区分肿瘤治疗有效或无效的有价值的影像指标。 FDG PET、扩散加权成像和动态增强MRI分别从肿瘤细胞代谢、肿瘤细胞密度以及肿瘤血流灌注方面来评价肿瘤治疗效果，为以解剖学为基础的高分辨率MRI提供了有益的补充。

Before and after neoadjuvant chemoradiotherapy, overall and accurate evaluation of locally advanced rectal cancer is associated with the selection of treatment schedule, while imaging diagnosis is the key point. Anatomical and functional MRI has been applied in the prediction and assessment of neoadjuvant chemoradiotherapy efficacy for locally advanced rectal cancer. Before neoadjuvant chemoradiotherapy, distance of ≤5 cm from the lower margin to anal verge and extramural venous invasion status assessed by high resolution MRI are independent predictors of tumor response to neoadjuvant chemoradiotherapy. After neoadjuvant chemoradiotherapy, MRI assessment of tumor regression grade （TRG） is a valuable imaging indicator to evaluate the response to neoadjuvant chemoradiotherapy. Furthermore, FDG PET, diffusion weighted imaging and dynamic contrast enhanced MRI can be used to evaluate the efficacy based on tumor cell metabolism, tumor cell density and tumor blood perfusion respectively, which provides helpful supplement for high resolution MRI based on anatomy.