Prior to accrual on the trial, patients with unresectable metastatic colorectal cancer will be treated with palliative chemotherapy. And patients who achieve a partial response or stable disease by imaging criteria will receive maintenance chemotherapy. In our study, these group patients will be randomized to maintenance chemotherapy or consolidative radiotherapy to all sites of disease (followed by maintenance chemotherapy at the medical oncologist's discretion). Choices of palliative and maintenance chemotherapy will be determined by the medical oncologist based on clinical appropriateness.