The Emergence of RAS Mutations in Metastatic Colorectal Cancer Patients Receiving Cetuximab Treatment

To evaluate the emergence of RAS mutation in patients with metastatic colorectal cancer, circulating free DNA will be analyzed using mass spectrometric genotyping in subjects during cetuximab treatment. The hypothesis of this study is that acquired RAS mutation is responsible for the resistance to cetuximab treatment in wild-type colorectal cancer. The usefulness of liquid biopsy to monitor dynamic genetic alterations in colorectal cancer during treatment will also be investigated in this study.