Radical treatment of primary rectal cancer with synchronous distant metastases includes surgical resection of primary and metastatic lesion. However, primary rectal cancer in case of metastasized disease are often locally advanced disease and need downsizing before surgery. It is reported that pelvic recurrence rates and distant metastasis rates outside liver are 30~35% and 60%, respectively. Therefore, combined treatment with radiotherapy and chemotherapy is used. However, the sequence of treatment modalities is not yet definitely established and preoperative chemoradiotherapy and surgical resection is accepted as an option of treatment. Conventional long course chemoradiotherapy delays administration of full-dose chemotherapy, and metastatic lesion can be progressed during chemoradiotherapy. In present study, we evaluate the efficacy of short course radiotherapy (SCRT) followed by full-dose chemotherapy with delayed surgical resection of the primary tumor and metastases.

Inclusion Criteria:

• Pathologically confirmed adenocarcinoma of rectum
• Lower margin of tumor within 12 cm from anal verge
• Clinically locally advanced (T3-4 or N1-2) disease
• Potentially resectable and synchronous distant metastases in liver and/or lung. The resectability of metastatic lesions is determined by size, number, location, general condition, liver function, and lung function.
• Over 18 years
• Eastern Cooperative Oncology Group performance status 0-2
• Proper organ function (Hemoglobin ≥ 10 g/dl, Absolute neutrophil count (ANC) ≥ 1,500/mm3, Platelet ≥ 100,000/mm3, Creatinine ≤ 1.5 mg/dl, Clearance of creatinine >50 ml/min using Cockcroft-Gault formula, Bilirubin ≤ 1.5 x upper limit of normal (ULN), Liver enzyme (Aspartate aminotransferase/Alanine transaminase/Alkaline phosphatase) ≤ 2.5 x ULN)
• Subject who should sign on the informed consent form before participate the trial.

Exclusion Criteria:

• Metastases in other organ except liver or lung
• History of other type of malignancies within 3 years other than non-melanoma of the skin or carcinoma in situ of cervix
• Hereditary colorectal cancer (FAP, HNPCC, and etc)
• Bowel obstruction or impending bowel obstruction
• Uncontrolled severe illness, unsuitable to chemoradiotherapy (within 6 months, myocardial infarct, unstable angina, heart failure, uncontrolled arrhythmia, uncontrolled epilepsy, central nervous system disease, psychological disorder, and etc)
• Subject pregnant or breast feeding, or incapable of appropriate contraception
• Unresected synchronous colorectal cancer
• History of prior pelvic radiotherapy
• History of prior chemotherapy for colorectal cancer
• Great surgery within 4 week before study enrollment
• Participant in other trial within 4 week before study enrollment