Gene sequencing may be a feasible means of individualizing cancer treatment. By investigating the correlation between genetic profiles and treatment outcomes of chemotherapy, it may be possible to determine effective treatment strategies according to individual genotypes in cancer patients. Despite great advances in drugs for cancer treatment, treatment outcomes may be improved by analyzing genetic markers that indicate treatment efficacy. We report the treatment for a patient with metastatic colon cancer in which gene sequencing was used for the selection of an effective chemotherapy regimen. In addition, we describe the entire course of treatment, including the combination of surgical resection for local control and radiotherapy to eradicate distant metastases. This is a pilot report of the clinical use of gene sequencing for determining a treatment regimen. Further clinical trials are needed to optimize the personalization of cancer treatment.