Assessing Outcomes of Patients Treated With Re-Irradiation Utilizing Proton Pencil-Beam Scanning for Primary or Recurrent Malignancies of the Esophagus and Gastroesophageal Junction.

Re-irradiation (re-RT) for locoregionally recurrent esophageal and gastroesophageal junction (GEJ) cancer and de novo esophageal + GEJ cancer arising in-field after a course of prior radiation poses considerable treatment challenges given the sensitivity of surrounding organs at risk (OARs). Guidelines for treatment of this presentation are not well established. Pencil-beam scanning (PBS) proton therapy has the ability to decrease radiation dose to OARs relative to photon plans. We present the first published series to date of re-RT with PBS for esophageal + GEJ malignancies and hypothesize that re-RT with proton PBS will be feasible and improve the safety profile of re-RT for this cohort of patients. Consecutive esophageal + GEJ cancers treated with PBS re-RT within a single institution were analyzed. Comparative volumetric-modulated arc therapy photon plans were generated. A total of 17 patients were included for analysis. At a median follow-up of 11.6 months, 1-year local control was 75.3% and overall survival was 68.9%. There were five (27.8%) grade 3 or higher late toxicities. When matched for clinical target volume coverage, proton PBS plans delivered significantly lower doses to the spinal cord, lungs, liver, and heart (all p < 0.05); five volumetric-modulated arc therapy plans would have been undeliverable on the basis of physician-specified OAR constraints. Re-RT for de novo or recurrent malignancies of the esophagus + GEJ, when delivered with PBS proton therapy, yields high rates of local control with acceptable acute and late toxicities in a high-risk population and decreased radiation dose to OARs relative to comparative photon plans. This is the largest series of proton re-RT for esophageal malignancies and the first that exclusively used PBS.

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