Efficacy and safety analysis of consolidation immunotherapy following definitive concurrent chemoradiotherapy for locally advanced esophageal squamous cell carcinoma

Background Definitive concurrent chemoradiotherapy (dCRT) is standard for locally advanced esophageal squamous cell carcinoma (ESCC), but recurrences remain common. Evidence for consolidation immunotherapy after dCRT is limited. This study evaluated the efficacy and safety of consolidation immunotherapy after dCRT and explored the association between programmed death-ligand 1 (PD-L1) expression and treatment outcomes. Methods This multicenter retrospective cohort included ESCC patients who completed dCRT without progression and received consolidation chemotherapy alone or with a programmed death-1 (PD-1) inhibitor followed by maintenance (July 2019–December 2024). Inverse probability of treatment weighting (IPTW) adjusted for baseline differences. Overall survival (OS), progression-free survival (PFS), objective response rate (ORR), and treatment-related adverse events (TRAEs) were compared. PD-L1 expression was assessed by combined positive score (CPS) in evaluable tissue. Results Among 96 patients, 45 received consolidation chemotherapy plus a PD-1 inhibitor followed by maintenance and 51 received consolidation chemotherapy alone. Median OS (43.1 vs. 26.0 months; P = 0.014) and PFS (25.4 vs. 9.6 months; P = 0.014) were longer with immunotherapy. After IPTW, OS (37.6 vs. 25.6 months; P = 0.018) and PFS (12.7 vs. 9.2 months; P = 0.037) remained significant. ORR was higher with immunotherapy (60.0% vs. 27.4%; P = 0.001). PD-L1 was evaluable in 38 patients; subgroup analyses were exploratory. Grade ≥3 TRAEs did not differ significantly (17.8% vs. 23.5%; P = 0.660). Conclusion Consolidation chemotherapy plus a PD-1 inhibitor followed by maintenance after dCRT was associated with longer OS and PFS in locally advanced ESCC, with comparable grade ≥3 TRAEs. PD-L1 analyses were inconclusive because few patients had evaluable tissue. These findings require validation in larger cohorts.