Evaluating the optimal radiation dose for definitive chemoradiotherapy for esophageal squamous cell carcinoma A single institution experience

The optimal radiation dose for definitive chemoradiotherapy in inoperable esophageal squamous cell carcinoma (ESCC) has been long debated. In this study, we evaluated the effect of doses greater than the conventional radiation dose (50.4 Gy) on tumor control, tumor response, overall survival (OS), and disease-free survival (DFS). The database of patients diagnosed with inoperable ESCC from 2007 to 2015 was obtained from the cancer registry of Chi-Mei Medical Center. All categorical variables were compared using Chi-squared test. The risk of OS and DFS were estimated using Cox proportional hazards regression, and Kaplan-Meier plots presented the trend of OS and DFS with log-rank tests used to compare differences. All significance levels were set at P<.05. A total of 84 patients were retrospectively analyzed, with 42 (50%) receiving > 50.4 Gy and 42 (50%) receiving <= 50.4 Gy (50%) concurrently with chemotherapy. Univariate and multivariate analysis revealed no significant differences between higher dose and conventional dose in OS (P=.21) and DFS (P=.26). Further dose analysis of < 50, 50 to 50.4, 51 to 60, and > 60 Gy showed no significant differences in OS or DFS. Higher doses conveyed no significant benefit on the failure pattern, either local regional failure or distant failure (P=.42). Major prognostic factors associated with better OS on multivariate analysis were stages I and II patients (P=.03) and radiation technique using arc therapy (P=.04). No acute toxicity of grade III or higher was recorded. The results of our study show that providing higher than conventional radiation doses concurrent with chemotherapy for inoperable ESCC does not impact OS or DSF, nor does it improve locoregional failure or distant failure. Although tumor response might be improved by radiation doses > 50.4 Gy, the impact on OS and DFS remain to be studied.