ARM I: Patients receive mFOLFOX6 regimen consisting of oxaliplatin intravenously (IV) over 2 hours, leucovorin calcium IV over 2 hours on day 1, and fluorouracil IV continuously over 46-48 hours on days 1-2. Treatment repeats every 2 weeks for 8 courses in the absence of disease progression or unacceptable toxicity. 3-4 weeks after last does of mFOLFOX6 patient undergo radiation therapy and receive capecitabine orally (PO) twice daily (BID) Monday-Friday for 5 weeks in the absence of disease progression or unacceptable toxicity.