[Chemoradiotherapy with S-1 for Recurrence Cases of Colorectal Cancer]

Although chemotherapy is the main treatment for recurrent colorectal cancer, the utility of radiotherapy as a local treatment has been widely reported. We performed chemoradiotherapy with S-1 for cases with recurrence after surgery, and the outcomes are reported herein.

Chemoradiotherapy with S-1 was performed in 4 cases. S-1 was administered for 2 weeks during the irradiation period, and the off period provided was 1 week.

X-ray irradiation was performed in 2 cases and proton beam irradiation in the other 2. The progression free periods of the 2 cases receiving proton beam irradiation were 31 months and 36 months. In contrast, the progression free periods of the 2 cases given X-ray irradiation were 24 months and 21 months.

It is known that S-1 not only achieves a high anticancer effect via dihydropyrimidine dehydrogenase(DPD)inhibition, which is a major metabolic pathway of 5-FU, but also increases the radiation susceptibility of malignancies. S-1 is regarded as an ideal anticancer agent when used in combination with radiation therapy. Since the local control achieved in our 4 cases was good, chemoradiotherapy with S-1 was considered to be a useful treatment.