A large retrospective study of 202 patients (90 inoperable patients and 100 patients (49.5%) had stage III/IV cancer) who were treated with PBT in Japan. This study reported that the 3-year and 5-year overall survival rate was 66.7% and 56.3%. The five-year local control rate was 64.4%. There were two patients with grade three pericardial effusion (1%) and a patient with grade three pneumonia (0.5%).

No grade 4 or higher cardiopulmonary toxicities were observed. The authors concluded that PBT for esophageal cancer was not inferior in efficacy and had lower rates of toxicities in comparison to photon radiotherapy.