The purpose of this study is to assess the safety and efficacy of S-1 and oxaliplatin combined with radiation by Phase I/II study.

The purpose of this study is as follows,

• In phase I, to determine the dose limiting toxicities (DLTs) and the maximum tolerated dose (MTD).
• In phase II, to evaluate the antitumor effect (pCR rate) and the safety .

Inclusion Criteria:

1. Patients with confirmed locally advanced and non-metastatic rectal adenocarcinoma (clinical stage T3, anyN or T4, anyN)
2. Possible to R0 resection
3. Received no prior therapy
4. Performance status (ECOG) 0-1
5. Normal organ and marrow function.
6. Sufficient oral intake

Exclusion Criteria:

1. History of serious allergic reaction
2. Patients without serious complications such as sensory neurotoxicity or serious diarrhea (with watery stool).
3. Female with pregnancy or lactation
4. Have another malignancy in the past 5 years except early stage other cancer that cure by local treatment