Goals and Background: There are great differences between treatment methods for early-stage esophageal cancer in institutions. Radiation therapy has been considered to be an effective modality as organ-preserving treatment of the disease. The aim of this study is to assess the effect and limitation of radiation therapy on patients with early esophageal cancer. Study: The subjects were 38 patientswith stage I (T1N0M0) squamous cell carcinoma of the esophagus who had received definitive radiation therapy alone. Eleven tumors were assessed within the mucosal layer, whereas 27 tumors showed submucosal invasion by examination using endoscopic ultrasound. All patients were treated with more than 60 Gy using a conventional daily fractionation dose at 2 Gy. An additional boost with brachytherapy was performed for 20 patients, and the prescribed doses were 10 Gy (5 Gy ×2 times) with low dose rate (8 patients) and 9 Gy (3 Gy ×3 times) with high dose rate (12 patients). Outcomes and prognostic factors, including the efficacy of intraluminal brachytherapy, were investigated. Results: The cause-specific survival rate and the local control rate at 5 yearswere 82.6%and 86.3%, respectively. Recurrences were noted in 8 patients with submucosal cancer, but no recurrence was observed in patients with mucosal cancer. In the present study, tumor length was a statistically significant prognostic factor for cause-specific survival (P = 0.018) and tumor depth tended toward statistical significance (P = 0.073). In 27 patientswith submucosal cancer, the tumor length was also statistically significant for the survival (P = 0.032). The 5-year cause-specific survival rates for the short tumor group and the long tumor groupwere 85.7%and 55.6%, respectively. On the other hand, the use of intraluminal brachytherapy had no significant effect on patient survival. Conclusion: Radiation therapy is very effective for early esophageal squamous cell carcinoma with tumor length less than 5 cm, but other treatment modalities, including chemoradiotherapy especially for inoperable patients, should be considered for submucosal cancer with a tumor length of 5 cm or more. Goals and Background: There are great differences between treatment methods for early-stage esophageal cancer in institutions. Radiation therapy has been considered to be an effective modality as organ-preserving treatment of the disease. The aim of this study is to assess the effect and limitation of radiation therapy on patients with early esophageal cancer. Study: The subjects were 38 patients with stage I (T1N0M0) squamous cell carcinoma of the esophagus who had definitive radiation therapy alone. Eleven tumors were assessed within the mucosal layer, All patients were treated with more than 60 Gy using a conventional daily fractionation dose at 2 Gy. An additional boost with brachytherapy was performed for 20 patients, and the first dose doses were 10 Gy (5 Gy × 2 times with low dose rate (8 patients) and 9 Gy (3 Gy × 3 times) with high dose rate (12 patients). Outcomes and prognostic Factors, including the efficacy of intraluminal brachytherapy, were investigated. Results: The cause-specific survival rate and the local control rate at 5 yearswere 82.6% and 86.3%, respectively. Recurrences were noted in 8 patients with submucosal cancer, but no recurrence was observed in patients with mucosal cancer. In the present study, tumor length was a significant lesserostic factor for cause-specific survival (P = 0.018) and tumor depth tended toward statistical significance (P = 0.073). In 27 patientswith submucosal cancer, the The 5-year cause-specific survival rates for the short tumor group and the long tumor group were 85.7% and 55.6%, respectively. On the other hand, the use of intraluminal brachytherapy had no significant effect on patient survival. Conclusion: Radiation therapy is very effective for early esophageal squamous cell carcinoma with tumor length less than 5 cm, but other ttreatment modalities, including chemoradiotherapy especially for inoperable patients, should be considered for submucosal cancer with a tumor length of 5 cm or more.