BackgroundThis retrospective study was to assess and compare the toxicity and efficacy of concurrent chemoradiotherapy (CCRT) with S-1 or docetaxel and cisplatin in patients with locally advanced esophageal squamous cell carcinoma (ESCC).MethodsPatients with locally advanced ESCC who received CCRT with S-1 (70 mg/m2 twice daily on days 1–14, every 3 weeks for 2 cycles, S-1 group) or docetaxel (25 mg/m2) and cisplatin (25 mg/m2) on day 1 weekly (DP group) between 2014 and 2016 were retrospectively analyzed. Radiotherapy was delivered in 1.8–2.0 Gy per fraction to a total dose of 50–60 Gy. Treatment-related toxicities (Common Terminology Criteria for Adverse Events version 4.0), response rate, and survival outcomes were compared between groups.ResultsA total of 175 patients were included in this study (72 in the S-1 group and 103 in the DP group). Baseline characteristics were well balanced between the two groups. The incidence of grade 3–4 adverse events were significantly lower in the S-1 group than that of the DP group (22.2% vs. 45.6%, p = 0.002). In the DP group, elderly patients (> 60 years) had a significantly higher rate of grade 3–4 adverse events than younger patients (58.1% vs. 31.3%, p = 0.01). The objective overall response rate (complete response + partial response) was 68.1% in the S-1 group, and 73.8% the DP group (p = 0.497). The 3-year overall survival was 34.7% in the S-1 group, and 38.8% in the DP group (p = 0.422). The 3-year progression free survival in the DP group was higher than that in the S-1 group but without significant difference (33.0% vs. 25.0%, p = 0.275).ConclusionCCRT with S-1 is not inferior to CCRT with docetaxel and cisplatin and is better tolerated in in elderly patients with locally advanced ESCC.