Therapeutic results of proton beam therapy with concurrent chemotherapy for cT1 esophageal cancer and salvage endoscopic therapy for local recurrence

Background: Proton beam therapy (PBT) with concurrent chemotherapy is promising for esophageal squamous cell carcinoma (ESCC). The aim of study was to evaluate the outcome of concurrent chemo-proton therapy (CCPT), i.e., PBT with concurrent chemotherapy for cT1 ESCC and the salvage endoscopic therapy for local recurrence. Methods: Patients with clinical T1 ESCC who underwent CCPT (60 GyE) between April 2013 and April 2017 at the National Cancer Center Hospital East were investigated. The efficacy of CCPT at the primary site was evaluated via endoscopy; primary complete response (CR) was defined as disappearance of the tumor lesion/ulcer and absence of cancer cells on biopsy. Endoscopic evaluation was performed with the same protocol of conventional chemoradiotherapy. Local recurrence after CCPT was treated with endoscopic resection for cT1a and with esophagectomy or photodynamic therapy for cT1b+. Results: Of the 44 patients (median age, 70 years) that underwent CCPT, 43 patients (98%) achieved primary CR. Among the 44 patients, the 3-year overall survival rate was 95.2%. Five patients (11%) developed local recurrence without regional lymph node or distant metastasis and received endoscopic resection or photodynamic therapy. All five patients were alive with no recurrence after a median 23 months. Conclusions: The results suggest that CCPT is an effective treatment for cT1 ESCC and careful endoscopic follow-up allows preferable local control with salvage endoscopic treatment.