Abstract:

Precise preoperative staging of low rectal cancer assessed by imaging        WANG Yi. Department of Radiology，Peking University People's Hospital，Beijing 100044，China
Abstract    The goal of treatment strategy for patients who has low rectal cancer is preserving sphincter and function and keeping decrease of local recurrence and increase overall survival. In the result of narrow space between tumor and surrounding structure，the positive resection margin increases the local recurrence in patient with low rectal cancer. Magnetic resonance imaging (MRI) preoperatively predict circumferential resection margin according to the relationship between tumor and the low rectal cancer surgical resection plane. MRI，which has been validated by previous studies，low rectal plane assessment，reducing pCRM involvement and avoiding overtreatment through selective preoperative therapy and rationalized use of permanent colostomy. However，surgical treatment of low rectal cancer is controversial，and one of the reasons is the lack of definition and standardization of surgery in low rectal cancer. Classification of low rectal cancers and standardization of surgery according to distance between lowest edge of tumor and depth of tumor invasion permit sphincter and function preserving surgery in of patients with low rectal cancer. In patients with rectal cancer who achieve clinical complete response after neoadjuvant chemoradiotherapy，“watch and wait” is a novel management strategy with potential to avoid major surgery. However，how to select proper candidates and how to assess the complete clinical response need further research.

Key words: low rectal cancer, operation, magnetic resonance imaging, staging

摘要：

低位直肠癌治疗的目标是降低局部复发率和延长生存期，同时尽可能保留括约肌结构和功能。由于肿瘤与周围结构间隙狭窄而导致手术切缘阳性，将增加低位直肠癌病人局部复发率。MRI通过分析低位直肠癌与周围结构的关系，可预测环周切缘是否为阳性。根据MRI检查结果调整手术切面，有助于降低手术切缘病理阳性率和局部复发率；同时，应用MRI判断切缘阴性而采用单纯手术方式，也可避免新辅助放化疗的毒副反应。然而，治疗策略中的手术方式选择并未达成共识，其原因之一是缺乏低位直肠癌手术定义和规范。高分辨率MRI可通过判断低位直肠癌下缘与肛直肠环上缘的纵向位置关系，以及低位直肠癌向肠壁外浸润深度的横向位置关系，协助确定手术方式，精准选择病人进行适宜的手术，增加了保留括约肌结构和功能的机会。在手术不断精细化和局部化的趋势下，通过新辅助治疗或完全新辅助放化疗实现完全临床缓解后采用“等待观察”的非手术策略，有望成为保留器官及其功能的重要治疗方案之一。目前，病人的选择和完全临床缓解的判断尚处于研究中。

关键词: 低位直肠癌, 手术, 磁共振, 分期