Hematological Markers Predict Immune‐Related Adverse Events in Patients With Recurrent or Metastatic Squamous Cell Carcinoma of the Head and Neck Treated With Pembrolizumab

ABSTRACT Background In patients with recurrent or metastatic squamous cell carcinoma of the head and neck (R/M SCCHN), the correlation between hematological markers and treatment outcomes has been established. However, their predictive role in the development of immune‐related adverse events (irAEs) remains unclear. Methods We conducted a multicenter retrospective cohort study to evaluate whether pre‐treatment hematological markers—including neutrophil‐to‐lymphocyte ratio (NLR), platelet‐to‐lymphocyte ratio (PLR), lymphocyte‐to‐monocyte ratio (LMR), and the CRP‐albumin‐lymphocyte (CALLY) index—predict the development of irAEs in 147 patients with R/M SCCHN treated with pembrolizumab. Results Lower NLR and PLR, as well as higher LMR and CALLY index, were significantly associated with a higher incidence of irAEs. Furthermore, NLR and LMR were significantly correlated with the occurrence of severe (Grade ≥ 3) irAEs. Conclusion Pre‐treatment NLR, PLR, LMR, and CALLY index may serve as useful predictive markers for the development of irAEs in patients with R/M SCCHN treated with pembrolizumab.