CT and MRI in the diagnosis of rectal cancer staging ZHANG Xiao-peng, SUN Ying-shi. Key Laboratory of Carcinogenesis and Translational Research, Department of Radiology, Cancer Hospital & Institute of Peking University, Beijing 100142, China
Correspondin author： ZHANG Xiao-peng, E-mail：zxp@bjcancer.org
Abstract    Rectal cancer is one of the most common causes of death from cancer. Accurate staging is necessary for optimal treatment. Preoperative staging is an essential factor in the multidisciplinary management of rectal cancer now because tumor stage is the strongest predictive factor for recurrence. The tumor node metastasis (TNM) system is used to describe numerically the anatomical extent of cancer. Various diagnostic methods provide accurate staging. Endorectal ultrasound (EUS) and magnetic resonance tomography  are suitable for determining tumor T stage. US is better for T1~2 stage tumor especially. Moreover, MRI has some advantages in T and N stage of advanced rectal cancer. Modern multidetector row CT is predestined for detecting distant metastases as it is a widespread, fast, and reproducible method. MRI is highly accurate in predicting the circumferential resection margin. MRI provides accurate assessment of the tumor relative to the circumferential margin, that is, the mesorectal fascia, the anal and pelvic peritoneal fold, which is valuable for determining therapy protocol and therapy outcome.