BACKGROUND/AIM: To evaluate the utility of endoscopy for assessing radiation esophagitis during chemoradiotherapy (CRT) with proton beam therapy (PBT) boost for esophageal cancer.

METHODS

Between December 2012 and December 2016, 38 patients with esophageal cancer were treated with CRT with PBT boost. To evaluate radiation esophagitis, endoscopy was performed after administration of CRT with standard PBT boost (total dose 50-60 Gy relative biological effectiveness [RBE]). Radiation esophagitis was evaluated and classified into 5 newly developed endoscopic grades (Fukui Acute Radiation Esophagitis [FARE] grade). The additional PBT boost was then adjusted and delivered (2-20 Gy [RBE]) to a maximum total dose of 74.4 Gy (RBE) based on the degree of radiation esophagitis, probability of residual tumor, and patient's general condition. To evaluate the utility of endoscopic examination, the incidences of adverse events graded according to National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE, version 4.0) were determined at the time of endoscopic examination after CRT with standard PBT boost (50-60 Gy [RBE]) and at the completion of treatment (60-74.4 Gy [RBE]), as well as during the 90 days from the beginning of treatment.

RESULTS

There was a significant correlation between FARE grade and CTCAE esophagitis grade (ρ = 0.48; p = 0.03). Moreover, endoscopy detected severe esophagitis in an asymptomatic patient. Radiation dose escalation was achieved without severe acute adverse events. There was no significant difference between the incidence of acute toxicity at the time of the CRT with standard PBT boost (50-60 Gy [RBE]) and the higher dose at the completion of treatment (60-74.4 Gy [RBE]), which suggests this dose escalation strategy is safe.

CONCLUSION

Endoscopic evaluation of radiation esophagitis using FARE grades was safely performed and useful for adjusting added radiation to ensure the safety of escalations in CRT with PBT boost for esophageal cancer.