The purpose of this study is to design a prospective randomized clinical trial to explore whether postoperative adjuvant chemotherapy may provide survival benefit for stage II colon cancer patients with high risk factors.Therefore the investigators can provide high level clinical evidence of indications for patients with colon cancer with stage II colon cancer.

The most controversial of adjuvant chemotherapy for colon cancer is whether stage II colon cancer should receive adjuvant chemotherapy or not. Because of the absolute little benefit of adjuvant chemotherapy after curative resection of stage II colon cancer，NCCN and ESMO guidelines do not recommend routine adjuvant chemotherapy for patients with stage II colon cancer unless combined with high risk factors.

Currently，most studies about stage II colon cancer with high risk factors were retrospective. Some suggested that patients with stage II colon cancer can benefit from adjuvant chemotherapy, however, more got the negative conclusions.

The study was designed as a multicenter, prospective, randomized, controlled trial.Patients who agreed to participate in the study would be randomly assigned to a treatment group of adjuvant chemotherapy or observation with 50% chance by a central randomization system determined by the computer program.

After a follow up of at least 3 years, the disease free survival of the two groups will be compared.

Inclusion Criteria:

1. aged 18 to 75 years;

2. pathologically confirmed adenocarcinoma of the colon

3. after curative resection pathological stage was T3-4N0M0;

4. with at least one of the following factors:

   1. T4 staging
   2. lymph nodes number less than 12
   3. poor differentiation (except MSI-H)
   4. LVI or PNI
   5. obstruction or perforation
   6. Elevated preoperative serum CEA

5. ECOG Performance status 0-1

6. no evidence of distant metastases

7. no preoperative chemotherapy or chemoradiation therapy

8. ANC > 1.5 cells/mm3, HGB > 10.0 g/dL, PLT > 100,000/mm3, total bilirubin ≤ 1.5 xULN, AST≤ 3 x ULN, ALT ≤ 3 x ULN.

9. Patients must read, agree to, and sign a statement of Informed Consent prior to participation in this study.

Exclusion Criteria:

1. combined with other cancer
2. Creatinine level greater than 1.5 times the upper limit of normal.
3. Patients who have received preoperative chemotherapy or chemoradiotherapy.
4. Patients with a history of a prior malignancy within the past 5 years.
5. Women who are pregnant or breast-feeding.
6. patients may not complete the whole schedule of chemotherapy
7. Patients with any other concurrent medical or psychiatric condition or disease which would make them inappropriate candidates for entry into this study.