功能磁共振成像对直肠癌新辅助放化疗疗效预测的价值

Value of functional magnetic resonance imaging in predicting outcomes of neoadjuvant chemoradiotherapy in rectal cancer

新辅助放化疗目前已成为局部进展期直肠癌（cT3或cN＋）的标准治疗方式，对新辅助治疗疗效的准确评估可指导合理治疗策略的选择。MERCURY临床试验证实，新辅助放化疗后常规磁共振成像（MRI；T2加权像）评估的肿瘤退缩分级与患者预后密切相关，同时其对于环周切缘的评估可指导全直肠系膜切除术的实施。相较于常规MRI检查，功能MRI（包括弥散加权成像及动态增强成像）在治疗疗效的预测方面效果更佳。MRI弥散加权成像（如治疗前后表观弥散系数的增加值）可提高再分期的准确性及对完全缓解的甄别。MRI动态增强成像可反映肿瘤内血管微环境，其动态灌注变化（如变化速率常数K21和容积转运常数Ktrans）可反映治疗疗效。功能MRI将在预测治疗反应和指导临床选择上发挥重要的作用。

Rectal cancer is one of the common cancers which poses a threat to the health of mankind. In recent years. Multi-modality treatment strategies for locally advanced rectalcancer improve the treatment efficiency. Accurate prediction of the treatment response after the neoadjuvant chemoradiotherapy （CRT） can guide more suitable treatment strategy. MERCURY study proved the prognostic value of post-CRT standard morphologic MRI（T2-weighted） assessment of tumor regression grade（TRG）, and MRI assessment of circumferential resection margin can guide the definitive surgery. Compared with standard morphologic MRI （T2-weighted）, functional MRI, including diffusion weighted imaging （DWI） and dynamic contrast enhanced （DCE） MRI, has shown more promising results for the prediction of therapeutic response in rectal cancer. The addition of diffusion-weighted images to T2- weighted images improves the accuracy of restaging examinations for determination of complete pathologic responders. DCE can reflect the tumor micro-vascular environment, and the change of perfusion in response to treatment. These images have the potential to improve the accuracy of therapeutic response in rectal cancer.