A prospective, non-interventional, observational, approach will be employed. All patient follow-up visits and other interactions will be established by the physician investigator: the CHOICE Registry will not impose a fixed schedule of follow-up visits. Data will be obtained in conjunction with actual follow-up visits to support treatment and various assessments of disease progression, patient quality of life and caregiver burden, and resource utilization. Patients will be followed for minimum of 15 months. All prescribed and administered medications, treatment adjustments and duration will be documented by the physician investigator treating the patient as per standard of care. The CHOICE Registry will not impose any change to the treatment regimen prescribed by physicians participating in the Registry. Adult males and females with metastatic colorectal cancer (having received first and second line treatment, and upon initiation of third line or later treatment) will be eligible to participate. Approximately 1000 patients will be enrolled by approximately 30 to 40 physician investigators representing both community and academic medical centers in the United States. Descriptive statistics will be employed to address the key research objectives of the CHOICE Registry, such as a description of patients receiving various second (and/or subsequent) lines of treatment in the management of metastatic colorectal cancer in real world clinical settings, and the associated clinical, economic, and humanistic (patient-reported) outcomes.