Efficacy of local consolidative radiotherapy with first-line chemoimmunotherapy in synchronous oligometastatic esophageal squamous cell carcinoma.

Background: Synchronous oligometastatic esophageal squamous cell carcinoma (SOESCC), characterized by a limited number of metastases at diagnosis, represents a significant subset of esophageal squamous cell carcinoma. However, the optimal treatment modality for the condition has not been determined. Therefore, we aimed to evaluate the efficacy of local consolidative radiotherapy (cRT) for the primary tumor combined with first-line chemoimmunotherapy (CIT). Methods: This retrospective cohort study included 102 patients with SOESCC who underwent first-line CIT, either alone or in combination with cRT, between 2018 and 2022. We analyzed the progression-free survival (PFS) and overall survival (OS) in the two groups using propensity score matching (PSM). Univariate and multivariate Cox regression analyses were performed to identify prognostic factors associated with PFS and OS. Failure patterns were compared between groups. Results: Patients who received the additional cRT had longer PFS (median PFS, 11.5 vs. 8.3 months, P = 0.009) than did those who received CIT only; however, no significant difference was noted in OS (median OS, 20.0 vs. 17.0 months, P = 0.410) between the two groups. These results remained consistent after PSM and multivariate Cox regression analyses (PFS: hazard ratio [HR] 0.539, 95% confidence interval [CI], 0.312-0.932, P = 0.027; OS: HR, 0.580, 95% CI, 0.307-1.095, P = 0.093). Notably, the pattern of failure in the CIT group was primarily characterized by locoregional failure, in contrast to the distant failure observed in the CIT + cRT group. Locoregional failure-free survival in the CIT + cRT group was significantly lower than that in the CIT group (P < 0.001). Moreover, no statistically significant difference was observed in the incidence of treatment-related adverse events between the two groups. Conclusions: In patients with SOESCC, the combination of local cRT and first-line CIT prolonged PFS without increasing treatment-related toxicity. In addition, cRT for primary tumor significantly reduced the incidence of locoregional failure. This synergistic approach appears to be a viable and potentially superior treatment strategy for the treatment of SOESCC.