A Study of Second- and Later-line Palliative Chemotherapy in Patients With Metastatic Colorectal Cancer.

Inclusion Criteria: * Patients who have signed the informed consent after receiving information about the purpose and method of this study. * Patients with histologically and radiologically confirmed metastatic colorectal cancer (colorectal cancer) who have evaluable (measurable) lesions. * Patients scheduled to receive their first second-line palliative chemotherapy following failure of first-line palliative chemotherapy (including those who relapse during or within 6 months after completion of postoperative adjuvant therapy, necessitating palliative chemotherapy). * Patients who understand the research, are cooperative in the research process, and are deemed capable of participating until the completion date. Exclusion Criteria: * Female patients who are pregnant, have childbearing potential, or are breastfeeding. * Has received an investigational product within 4 weeks from the study enrollment or has plans to participate in another clinical trial during the participation of this study. * Other subjects who are considered inappropriate to participate in this study by the judgment of the investigator.