Fig. 1

Endoscopic examination prior to and after carbon-ion radiotherapy. a Upper gastrointestinal endoscopy showing a type 0-IIa + 0-IIc lesion located 27–29 cm from the incisors. b Chromoendoscopy with iodine staining revealing a lugol-voiding lesion with distinct margin. c Dose distribution of the carbon-ion radiotherapy. The isodose line of 95% is indicated by the orange line. d Examination 4 months after carbon-ion radiotherapy. The patient achieved a complete response