Concurrent chemoradiotherapy with S-1 as first-line treatment for patients with oropharyngeal cancer

Purpose: S-1 is an oral fluoropyrimidine. The purpose of this study was to review the clinical outcomes of S-1 with concurrent radiotherapy for patients with oropharyngeal cancer. Materials and Methods: Between 2002 and 2007, 38 patients with oropharyngeal cancer treated concurrently with S-1 and definitive radiotherapy were reviewed. The clinical stage was Stage I in 4 patients, Stage II in 7, Stage III in 7, and Stage IV in 20. S-1 was administered orally twice daily for 4 consecutive weeks followed by a 2-week drug withdrawal. The initial dose of S-1 was 65 mg/m2/day. All patients were treated using three-dimensional conformal radiotherapy with a median total dose of 65.1 Gy (range, 60.0-71.0 Gy). Clinical outcomes and major acute toxicities were analyzed based on medical records and clinical follow-up. Results: With a median follow-up time of 33 months, the 3-year estimates of local-regional control, distant metastases-free survival, disease-free survival, and overall survival for all patients were 75%, 80%, 65%, and 80%, respectively. The 3-year estimates of local-regional control according to stage were 100% for Stages I and II, 86% for Stage III, and 56% for Stage IV. The rate of ≥ Grade 3 acute mucositis was 32%, and the rate of ≥ Grade 3 hematological toxicities was 8%. No other severe toxicities were observed. Conclusions: Concurrent chemoradiotherapy with S-1 was found to be effective, especially for early disease. The treatment-related toxicities were acceptable, and the incidence of myelotoxicity was low. Further study must be carried out to compare with other chemotherapy regimens.