Phase I study of oral S-1 and concurrent radiotherapy in patients with head and neck cancer

This study investigated the maximum tolerated dose (MTD) of S-1 with concurrent radiotherapy in patients with head and neck cancer, based on the frequency of dose-limiting toxicities (DLT). S-1 was administered orally at escalating doses from 40 mg/m(2) b.i.d. on the days of delivering radiotherapy, which was given at a total dose of 64–70 Gy in 32–35 fractions over 6–7 weeks. A total of 12 patients (3 patients at 40 mg/m(2), 6 patients at 60 mg/m(2), and 3 patients at 80 mg/m(2)) were enrolled in this trial. At the dose of 80 mg/m(2), two of the three patients developed DLT (Grade 3 anorexia and rhabdomyolysis) due to S-1, so the MTD was determined to be 80 mg/m(2). Among the 12 enrolled patients, 9 (75%) showed a complete response and 3 (25%) showed a partial response. The overall response rate was 100%. The recommended dose of S-1 with concurrent radiotherapy is 60 mg/m(2).