Maintenance Chemotherapy After Neoadjuvant Chemoradiation Therapy for Distal Rectal Cancer

Inclusion Criteria: * over 18 years old * tumor potentially resectable en bloc; tumors tethered or fixed to a structure that can be removed * clinical/radiological stages T2,T3,or T4, N0-1 * ANC \>1500, PLT\>100,000 * AST and alkaline phosphatase \< 2.5 X ULN * bilirubin \< 1.5 X ULN * CrCl \> 50 ml/min using Cockcroft-Gault formula * KPS \>60 * ECOG Performance Scale 0-2 * No malignancies within previous 5 years other than non-melanoma skin cancer, in-situ cervical cancer, in-situ ductal breast cancer * no evidence of metastatic disease Exclusion Criteria: * initial tumor fixation to pelvic bone or side wide; technically unresectable disease * any evidence of distant metastasis * perforation * obstruction * hereditary non-polyposis colorectal cancer * synchronous primary colon carcinomas except T1 lesions * known dihydropyrimidine dehydrogenase deficiency * prior radiation therapy to the pelvis * prior chemotherapy for malignancies * known existing uncontrolled coagulopathy * pregnancy or lactation * women of childbearing potential not using reliable and appropriate contraceptive method * serious, uncontrolled concurrent infection(s) * participation in any investigational drug study within 4 weeks preceding the start of study treatment * clinically significant heart disease * other serious uncontrolled medical conditions that might compromise study participation (in the investigator's opinion) * major surgery within 4 weeks prior to the study treatment * lack of physical integrity of the upper GI tract or malabsorption syndrome