After neoadjuvant chemoradiotherapy(nCRT), 15%-40% of rectal cnacers has a pathological complete response (pCR), with non-malignant cells demonstrated in histological assessment of the surgical resection specimen. Since these patients have excellent oncological outcomes, there has been a rapidly growing interest in organ preservation for those who achieve a clinical complete response (cCR), that is "Watch and Wait strategy" (W&W). One of the major challenges in the W&W of rectal cancer is the careful and precise selection of patients suitable for this approach. The published series on W&W has all used different modalities to assess response post nCRT, including the MSKCC's three-tiered evaluation plan and Mercury's mrTRG criteria. Except significant heterogeneous results, the evidence available comes mostly from retrospective cohort studies, furthermore, there is a lack of data of long-term outcomes. How to accurately screen pCR patients preoperatively is an important and difficult issue of clinical concern.
局部进展期直肠癌经新辅助治疗后，有15%~40%的患者可达到病理学完全缓解（pCR），此类患者肿瘤相关结局极好。越来越多的研究表明，此类患者有可能避免根治性切除，代之以等待观察策略。施行等待观察策略的主要挑战之一就是如何准确识别pCR患者。目前，针对临床等待观察策略中完全缓解（CR）患者的检出，主要有两种不同的影像评估方案：一是美国纪念斯隆凯物琳癌症中心（MSKCC）提出的三维度评估方案；二是Mercury提出的核磁肿瘤退缩分级（mrTRG）标准。但现有的影像学评估方法存在显着异质性，证据主要来自回顾性队列研究，且缺乏长期生存的数据。如何在术前准确地筛查pCR患者，是临床关注的重点及难点问题。.
Keywords: Complete response; Imaging; Neoadjuvant therapy; Rectal neoplasms; Watch and wait strategy.