Immune-related adverse events as independent prognostic factors for camrelizumab in patients with esophageal squamous cell carcinoma: a retrospective cohort study

Background: While programmed cell death protein 1 (PD-1) blockade has demonstrated varying effectiveness in treating advanced esophageal squamous cell carcinoma (ESCC), no validated prognostic factors have been identified. Immune-related adverse events (irAEs) have been shown to predict immunotherapy outcomes in multiple cancers, but their relationship with ESCC remains unclear. This study aims to evaluate the prognostic value of irAEs in patients with advanced ESCC treated with camrelizumab. Methods: We conducted a retrospective chart review of patients with recurrent or metastatic ESCC who were treated with single-agent camrelizumab at the Department of Oncology and Hematology in China Japan Union Hospital of Jilin University between 2019 and 2022. The study's primary endpoint was objective response rate (ORR), while secondary endpoints included disease control rate (DCR), overall survival (OS), and safety. We used the chi-squared test and odds ratio (OR) to evaluate any relationships between the occurrence of irAEs and ORR. Prognostic factors for OS were identified through survival analysis using the Kaplan-Meier method and multivariate Cox regression. Results: The study included 136 patients with a median age of 60 years, of whom 81.6% were male and 89.7% received platinum-based chemotherapy as their first-line therapy. Among these patients, 128 irAEs were observed in 81 patients (59.6%). Patients who experienced irAEs achieved a significantly better ORR [39.5% vs. 14.5%; OR =3.84; 95% confidence interval (CI): 1.60-9.18; P=0.003] and longer OS [13.5 vs. 5.6 months; adjusted hazard ratio (HR) =0.56, 95% CI: 0.41-0.76; P=0.0013] than those who did not experience irAEs. Multivariate analysis identified the presence of irAEs as an independent prognostic factor for OS (HR =0.57, 95% CI: 0.42-0.77; P=0.0002). Conclusions: The presence of irAEs in ESCC patients treated with anti-PD-1 therapy (camrelizumab) may serve as a clinical prognostic factor, indicating improved therapeutic effectiveness. These findings suggest that irAEs could be used as a potential marker to predict outcomes in this patient population.