Efficacy of Omalizumab against Japanese Cedar pollinosis in clinical practice.

BACKGROUND: Japanese cedar pollinosis (JCP), which affects over 40% of the population and represents a major public health issue in Japan, has various treatment options, but limited clinical reports and high costs necessitate careful patient selection. This study aimed to evaluate the efficacy of omalizumab in treating JCP and identify key considerations for its appropriate clinical application. METHODS: We retrospectively analyzed 42 patients with JCP treated with omalizumab from 2021 to 2024. Treatment response was assessed using a 3-category patient-reported scale across all years. In a 2023-2024 subset (n = 23), quantitative total symptom score (TSS) data were available, allowing effect-size estimation and subgroup analyses. RESULTS: The study included 42 patients (30 men, 71.4%) aged 12-80 years (mean, 41.5 ± 17.2 years). Symptom improvement was observed in 38 patients (90%), including marked improvement in 23 (55%). Responders were younger (mean age 39.9 vs. 55.5 years) and had higher total IgE levels (251 vs. 211 IU/mL) than nonresponders. No significant correlation was observed between nasal eosinophil counts and treatment response. In the 2023-2024 subset (n = 23), TSS decreased significantly (mean paired difference - 2.61; p = 0.0010). Subgroup analyses suggested that CRSsNP cases tended to show insufficient improvement, while younger age and higher IgE levels were associated with better response trends. CONCLUSIONS: Omalizumab significantly improved symptoms and QOL in patients with JCP. However, its high cost and the risk of nonresponse necessitate careful patient selection. Age and IgE levels may help guide treatment decisions, highlighting the importance of individualized strategies for severe JCP.