Additional radiotherapy following endoscopic submucosal dissection for T1a-MM/T1b-SM esophageal squamous cell carcinoma improves locoregional control

Background: Endoscopic submucosal dissection (ESD) can be used as a less invasive treatment option for superficial esophageal cancer involving the muscularis mucosae (T1a-MM) or upper third of the submucosa (T1b-SM1). Additional treatment after ESD is needed to prevent lymph node metastasis. However, the efficacy of radiotherapy following ESD has not been well evaluated. Moreover, the clinical outcomes of patients with large mucosal defects of the esophagus who received radiotherapy after ESD have not been reported. This study aimed to clarify the efficacy of additional radiotherapy following ESD for esophageal squamous cell cancer involving T1a-MM or T1b-SM1. Methods: We analyzed twenty-seven patients with pathologically confirmed T1a-MM or T1b-SM1 esophageal squamous cell cancer treated by ESD. Thirteen patients received additional radiotherapy (RT group), and the remaining patients did not (non-RT group). Locoregional control (LRC), overall survival, cause-specific survival, and adverse events including treatment-related esophageal strictures were evaluated. Results: The three-year LRC was significantly better for the RT than the non-RT group (100% vs. 57.8%, respectively; p = 0.022). Chemotherapy following ESD did not improve LRC. Multivariate analysis showed that radiotherapy was an independent prognostic factor for better LRC (p= 0.0022). Contrary to the results in LRC, overall and cause-specific survival were not significantly different between the RT and non-RT groups. A subgroup analysis of patients with mucosal defects involving ≥ 3/4 of the esophageal circumference after ESD showed that LRC of the RT group was better than that of the non-RT group (p = 0.049). Treatment-related esophageal strictures were observed in 2 of 6 patients in the RT group with large mucosal defects after ESD. No patients with mucosal defects involving less than 3/4 of the circumference after ESD developed treatment-related strictures. Conclusions: Radiotherapy after ESD contributed to better LRC in esophageal squamous cell cancer involving pT1a-MM and pT1b-SM1. Esophageal strictures were observed in some patients with large mucosal defects after ESD. Despite leading to better LRC, radiotherapy after ESD should be undertaken after careful consideration for patients with large mucosal defects after ESD.