Hematological toxicity of immune checkpoint inhibitors: a pharmacovigilance study

Immune-related adverse events (irAEs) have limited the widespread clinical application of immune checkpoint inhibitors (ICIs). Hematological toxicities are rare but serious irAEs. This study comprehensively analyzes ICI-related hematological adverse events using the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS).database. We extracted ICI adverse events from the FAERS database between January 2004 and January 2025. Disproportionality analyses using four algorithms identified hematological signals. To eliminate the influence of combined medication, we separately conducted disproportionality analysis on all ICI reports and on reports of ICI monotherapy. Multivariable logistic regression was employed to assess the risk factors for hematological adverse events. Of all ICI reports in FAERS, 3.73% were for hematological adverse events. Among the 14 detected hematological signals, pure red cell aplasia, immune-mediated pancytopenia, acquired hemophilia, and Evans syndrome are rare and severe irAE. Among 6,259 cases of ICI-related hematological AEs, approximately 88.68% were reported by healthcare professionals, and fatal outcomes were reported in 16.49% of cases. The median onset time is 20 days.The median age of patients was 67 years (IQR: 58–73). Male was associated with a significantly lower risk of hematological toxicity compared to females (OR = 0.92, 95% CI: 0.90–0.96; P < 0.05). Patients aged ≥ 65 years also had a reduced risk compared to those < 65 years (65–74 years: OR = 0.64, 95% CI: 0.62–0.67; ≥75 years: OR = 0.75, 95% CI: 0.72–0.79; both P < 0.05 ). ICI combination with chemotherapy significantly increased the risk of hematological toxicity (OR = 3.56, 95% CI: 3.44–3.69; P < 0.05), while combination with targeted agents reduced the risk (OR = 0.73, 95% CI: 0.69–0.76; P < 0.05). To our knowledge, this is among the first studies to utilize real-world big data for disproportionality analysis focused on ICI monotherapy, uncovering rare and severe hematological irAE. Multivariable logistic regression revealed that following ICI treatment, females are at a higher risk than males for hematological toxicities; likewise, ICI–chemotherapy increases the risk compared to ICI monotherapy. Clinicians should pay more attention to these rare irAEs and identify and treat them as early as possible, especially in patients with high-risk factors.