Inclusion Criteria:

1. Histologically confirmed adenocarcinoma of the rectum

2. Patients who treated with preoperative chemoradiation with fluoropyrimidines followed
by curative surgery without microscopic residual tumor.

3. AJCC/UICC pathologic stages of ypT3-4 or ypN+

4. Curative surgery not less than 3 and not more than 8 weeks prior to randomization

5. No prior chemotherapy, radiotherapy and immunotherapy except preoperative
chemoradiation for rectal cancer

6. ECOG PS 0-1

7. Adequate organ function

8. Informed Consent

Exclusion Criteria:

1. Macroscopic or microscopic evidence of remaining tumor

2. Any histologic feature other than adenocarcinoma or arisen from chronic inflammatory
bowel disease

3. More than 8 weeks after curative surgery