Proton beam-based chemoradiotherapy versus surgery plus adjuvant chemotherapy for esophageal squamous cell carcinoma: a comparison of the long-term survival from a single-center cohort study

Summary Background Chemoradiotherapy using proton beam therapy is a novel and promising option for patients with esophageal squamous cell carcinoma (ESCC) who do not prefer surgical treatment. Materials and Methods This was a single-center retrospective cohort study. Patients diagnosed with thoracic ESCC, clinical Stages I, II, or III, who underwent definitive proton-based chemoradiotherapy (PBC) or surgery-based treatment (SBT) between 2009 and 2020 were included. Patients intolerant to surgery or palliative radiotherapy were excluded. PBC was defined as radical-intent chemoradiotherapy using a proton beam with chemotherapy, and a combination of photon radiation was allowed. SBT was defined as subtotal esophagectomy with lymph node dissection with or without adjuvant chemotherapy. The propensity score matching was performed using potential confounding factors as covariates. The primary endpoints were the hazard ratio (HR) and 5-year overall survival (5yOS). Results This study included 247 patients (112 with SBT and 135 with PBC). Survival outcomes were compared between the 95 patients in each group using propensity score matching. The mean observation period was 57.5 months. The 5yOS was 62.0% in the SBT and 55.3% in the PBT group (P = 0.421). The adjusted HR for PBC was 1.22 (0.79–1.90). No treatment-related deaths occurred in the PBC group. Serious adverse events included neutropenia (n = 5), esophageal ulcer (n = 3) in the early phase, and esophageal fistula (n = 3), pleural effusion (n = 1), and pericardial effusion (n = 1) in the late phase. Conclusion Radical chemoradiotherapy using proton beams is a promising treatment option for patients with ESCC who do not prefer surgery in terms of safety and efficacy.