Correlation between irAEs and treatment efficacy of anti-PD-1 single agent in patients with recurrent/metastatic head and neck squamous cell carcinoma: A monocentric real-world observational study.

6029 Background: Immune-related adverse events (irAEs) are associated with efficacy of ICIs-based treatment in various cancer types. The aim of this retrospective study was to assess the relationship between irAEs and outcomes in patients with recurrent/metastatic Head and Neck squamous cell carcinoma (R/M-HNSCC) treated with immune checkpoint inhibitors (ICIs) monotherapy. Methods: We retrospectively reviewed data from patients with R/M HNSCC treated with ICIs single-agent between January 2018 and June 2023 at the Istituto Oncologico Veneto of Padua. Common Terminology Criteria for Adverse Events v.5.0 was used to assess irAEs evaluation. Patients were stratified into irAEs (any grade) and non-irAEs groups. Overall survival (OS) and progression free survival (PFS) were assessed using the Kaplan-Meier method. Univariate and multivariate Cox-regression were used to compare survival outcomes. The chi-square test was used to assess the association between irAEs and objective responses (ORR). Results: A total of 89 patients were eligible for the analysis. Patients with platinum-refractory disease received nivolumab (64 patients, 72%). All the 25 patients (28%) with platinum-sensitive disease were PD-L1 positive (CPS≥1) and received pembrolizumab as first line treatment for R/M disease. Median follow-up was 8.7 months. IrAEs (any grade) were observed in 60 patients (67%), including 9 patients (10%) with grade ≥3 AEs. The most common irAEs were endocrinopathies (35%), skin events (15%), hepatic events (13%), diarrhea/colitis (10%) and lipase/amylase elevation (10%). The ORR was higher in the irAEs group than in the non-irAEs group (19.5% vs 2%, p=0.017). PFS and OS were also significantly longer in the irAEs group: median PFS was 3.9 months vs 2.1 months (HR 0.48 95% CI 0.30-0.77; p=0.003) and median OS was 12.5 months vs 4.3 months (HR 0.36 95% CI 0.21-0.60; p=0.000). The statistically significant benefit for both PFS and OS was confirmed at the multivariate analysis (Table1). Patients who experienced endocrine-related irAEs (p=0.004), diarrhea/colitis (p=0.040) and lipase/amylase increase (p=0.005) had significantly longer OS than those without the corresponding toxicity. A positive trend was observed for skin toxicity (p=0.051). Conclusions: The occurrence of irAEs was a predictor of response and survival outcomes in patients with R/M HNSCC treated with ICIs single-agent.Table: see text