TAS-102 significantly improves overall survival in patients with metastatic colorectal cancer. The most common adverse event of TAS-102 is bone marrow suppression, which leads to neutropenia. The incidence of neutropenia is high, and there is no known effective prevention method. Furthermore, the administration method of TAS-102 is complicated. We reported that neutropenia could be avoided by changing to a simple administration method of TAS-102.