Background: To date, intensity-modulated radiation therapy (IMRT) with concurrent chemoradiotherapy (CCRT) and CCRT with standard fractionation three-dimensional conformal radiation therapy (3D-CRT) have not been compared. In this study, the outcomes of IMRT-based concurrent CCRT and those of 3D-CRT-based CCRT were compared in patients with thoracic esophageal squamous cell carcinoma (TESCC). Methods: We enrolled 2062 patients with TESCC who had received CCRT and categorized them into two groups on the basis of their treatment modality: Group 1 (3D-CRT-based CCRT) and Group 2 (IMRT-based CCRT). Results: Multivariate Cox regression analysis indicated that the American Joint Committee on Cancer advanced stages (≥IIIA) and 3D-CRT were significant independent predictors of poor outcomes in patients with TESCC who received definitive CCRT. Moreover, receiving IMRT-based CCRT (adjusted hazard ratio [aHR]: 0.88, 95% confidence interval [CI]: 0.78–0.98) was a significant independent prognostic factor for overall survival (p = 0.0223). In Group 2, aHRs (95% CIs) for overall mortality at early (IA–IIB) and advanced clinical stages were 0.91 (0.67–1.25, p = 0.5746) and 0.88 (0.77–0.99, p = 0.0368), respectively. Conclusion: IMRT-based CCRT resulted in higher survival rates in patients with advanced clinical stages of TESCC (i.e., IIIA–IIIC), namely, clinical T3, clinical T4, or lymph node involvement.
