Safety Study of Capecitabine With Radiation in Elderly Rectal Cancer

Inclusion Criteria: * rectal adenocarcinoma, clinical stage II/III(T3-4 or N+, AJCC 7th). * KPS status no less than 70; Charlson comorbidity no more than 3. * life expectancy more than 6 months. * hemoglobin \>= 100g/L, white blood cell \>= 3.5\*10E9/L, neutrophil \>= 1.5\*10E9/L, platelet \>= 100\*10E9/L.Creatin normal, Total bilirubin normal, AST and AST normal, AKP normal. * do not have allergy history to thymidine phosphorylase. * do not receive surgery ( except palliative colostomy) or chemotherapy or other anti-cancer treatment * no previously pelvic irradiation history * informed consent signed Exclusion Criteria: * other cancer history, except curable non-melanoma skin cancer or cervix in-situ carcinoma * previous pelvic irradiation history * receiving surgery (except palliative colostomy), chemotherapy or other anti-cancer treatment * allergy history to thymidine phosphorylase * active infection existed * severe complication, such as acute myocardial infarction in 6 months, uncontrolled diabetes ( Plasma glucose concentrations in any time of a day≥11.1mmol/L）, severe cardiac arrhythmia， etc. * anticipate other clinical trials in four weeks before enrollment