609. LONG-TERM OUTCOMES OF SALVAGE SURGERY AFTER PROTON BEAM THERAPY FOR ESOPHAGEAL SQUAMOUS CELL CANCER

Abstract Background Proton beam therapy (PBT) for esophageal cancer is a promising option for local control, reducing adverse events. The salvage surgery is sometimes performed for residual or recurrent lesion after PBT, however the long-term outcome has not been known for lack of previous reports. Methods Of 374 patients treated with radical PBT for squamous cell carcinoma of the thoracic esophagus at our institution from 2009 to 2018, we selected cases in which salvage surgery was performed. Salvage surgery was defined as surgical resection of recurrent primary tumor and/or lymph node metastases. The primary outcome was overall survival, and secondary outcomes and postoperative complications were investigated. Results Nineteen patients in whom salvage surgery was performed were included. Median age was 66 (55-80) years, male: female: 16:3, clinical stage at initial presentation was I:II:III = 3:6:10, and median time from PBT to relapse was 23.8 months. Esophagectomy were performed in 12 patients, and lymphadenectomy for recurrent lymph node were performed in 7 patients. During a median observation period of 26.5 months postoperatively, 14 cases were confirmed to have died of primary disease, and the median overall survival from salvage surgery was 38.3 months. 8/14 (57.1%) patients had Grade 3 or higher postoperative complications, and no operative mortality was observed. Conclusion We showed the long and short-term outcome of salvage surgery after PBT for esophageal squamous cell carcinoma. Although the risk of postoperative complications was high, some cases of long-term survival after salvage esophagectomy were observed.