Inclusion Criteria:（1）Age: 18 ~ 70 years old; sex is not limited. （2）Patients with stage II/III rectal cancer staged under MRI or endoscopic ultrasonography and have at least one risk factor: cT4a-b(resectable)；cT3c-d with EMVI+ (Extramural venous invasion)；cN2；MRF+ (MRI in evaluating the mesorectal fascia).（According to the 2010 AJCC cancer staging system, the seventh edition）. The preoperative T stage is referred to endoscopic ultrasonography or rectal MRI. The N stage is referred to abdominal CT. The M stage is referred to abdominal and thoracic CT. If symptoms occur, other appropriate imaging examinations are needed（cranial MRI or ECT）.