Safety and Efficacy of Concurrent or Sequential Radiotherapy Plus (PD-1) Inhibitors in Oligometastatic Esophageal Cancer.

Purpose: We assess real-world outcomes, including safety and efficacy, of concurrent or sequential treatment with radiotherapy plus programmed cell death protein 1 (PD-1) inhibitors in patients with oligometastatic esophageal cancer (OMEC). Methods: This cohort study retrospectively collected clinical data of patients with synchronous or metachronous OMEC. All patients underwent concurrent or sequential treatment with radiotherapy plus PD-1 inhibitors. Each patient had up to five measurable metastatic lesions and up to three organs involved. Study endpoints were progression-free survival (PFS), treatment-related toxicities, locoregional progression-free survival (LRPFS), objective response rate (ORR), and disease control rate (DCR). Description statistics and Kaplan-Meier models were used for statistical analysis. Results: A total of 86 patients were included, most of whom were diagnosed with squamous cell carcinoma histology (98%) and presented with synchronous OMEC (64%). The median follow-up period was 17 months (range: 6-32 months), the median PFS was 15.2 months (95% confidence interval: 12.1-18.2 months); and the 1- and 2-year PFS rates were 61.4% and 26.7%, respectively. The 1- and 2-year LRPFS were 91.3% and 57.3%, respectively. The ORR and DCR were 46.5% and 91.8%, respectively. Forty-two patients (48.8%) experienced grade 3 or higher treatment-related adverse events (TRAEs); a grade 5 treatment-related adverse event was observed in one patient (1.2%) who died of immune-related pneumonitis. Conclusion: Combining radiotherapy with PD-1 inhibitors is a safe and effective treatment option for patients with OMEC. No new safety concerns were identified in this study. However, due to the potential risk of cumulative toxicity, an individual risk-benefit assessment for each patient is required prior to treatment initiation.