A Randomized, Prospective, Multicenter Study for the Role of Primary Tumor Resection in Colorectal Cancer Patients With Asymptomatic, Synchronous Unresectable Metastasis

Inclusion Criteria:

* Age : between 20 and 90 years old
* Histologically confirmed adenocarcinoma of the colon or the upper rectum
* Patients with resectable primary colon or upper rectal cancer and unresectable metastatic lesions.
* Patients with no primary cancer related symptoms.
* ECOG performance status of 0 - 2
* Appropriate organ functions (hepatic transaminases - less than 5 times the normal range; bilirubin - less than 2 times the normal range; creatinine serum - less than 1.5 times the normal range; thrombocyte - more than 100,000/µl; neutrophil - more than 1,500/µl)
* ASA score of \< 3
* An informed consent form has been signed by the patient.

Exclusion Criteria:

* The patient received adjuvant chemotherapy within the past 6 months.
* The patient received chemotherapy for metastatic colon cancer.
* The patient was planning to have curative surgery for the metastatic lesions.
* The primary cancer is unresectable.
* Patients with peritoneal carcinomatosis.
* Patients with mid and low rectal cancer (\< 10cm)
* Patients with primary tumor related complications such as intestinal obstruction, intractable bleeding, and perforation, that needs to be treated.
* ASA score of \> 4
* The patient has chronic hepatitis or cirrhosis. An asymptomatic HBV or HCV carrier can participate.
* Patients with an active infection, which need antibiotic therapy, during the randomization period.
* Pregnant or breastfeeding women
* Patients who were enrolled in another clinical trial during the time of enrollment (within the 28 day randomization period).
* Patients with another different malignant tumor during the past 5 years. Patients with treated non-melanoma skin cancer or cervical cancer can be enrolled in this study.