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.