Observational Study on the Patients With Rectal Cancer

Inclusion Criteria: * Aged older than 18 years * American Joint Committee on Cancer (six edition) stage I through IV disease * Received either transabdominal resection, transanal excision, preoperative radiotherapy or chemoradiotherapy * Had the histologic subtypes adenocarcinoma (not otherwise specified, mucinous or mucin-producing, mixed cell or with mixed subtypes, tubular, and papillary) Exclusion Criteria: * Had the histologic subtypes squamous cell carcinoma, carcinoid, neuroendocrine tumor, small cell carcinoma, leiomyosarcoma, sarcoma, gastrointestinal stromal sarcoma, melanoma, carcinosarcoma, rhabdoid tumors, or malignant peripheral nerve sheet tumors * Only receive palliative surgery such as colostomy, sigmoidostomy * Received palliative radiotherapy or chemoradiotherapy for metastatic disease * With unresectable distant metastasis in liver, lung, bone, central nervous system , or peritoneal transplantation * Had no detailed medical records