S-1 Monotherapy as Second- or Third-Line Chemotherapy for Unresectable and Recurrent Esophageal Squamous Cell Carcinoma

<b><i>Purpose:</i></b> S-1 is widely used for various cancers. It may be useful for esophageal squamous cell carcinoma (ESCC); however, there are insufficient data. The purpose is to provide results of an analysis of S-1 monotherapy for unresectable and recurrent ESCC. <b><i>Patients and Methods:</i></b> Twenty patients with histologically proven ESCC who were previously treated with other chemo(radio)therapies were treated with S-1 alone as second- or third-line chemotherapy. <b><i>Results:</i></b> A complete response (CR) was observed in 1 case (5%). A partial response (PR), stable disease (SD), and progressive disease (PD) were seen in 4 (20.0%), 7 (35.0%), and 8 (40.0%) cases, respectively. Two cases (10%) of anemia, 1 case (5%) of leukopenia, 3 cases (15%) of fatigue, and 3 cases (15%) of diarrhea were observed as grade 3 toxicity; however, there were no cases of grade 4 toxicity. The 1-year progression-free survival (PFS) rate was 10.0%, and the median PFS was 100 days. The 1-year overall survival (OS) was 30.5%, and the median OS was 330 days. The 1-year PFS rate in CR/PR/SD and PD was 16.7 and 0%, and the median survival time was 120 and 40 days. <b><i>Conclusion:</i></b> S-1 is a promising new drug which can be used as a second- or third-line chemotherapy for ESCC.