Type of publication:
Conference abstract
Author(s):
Carpo B.; *Arunachalam J.; Gunturu K.
Citation:
Journal of Thoracic Oncology. Conference: 2025 World Conference on Lung Cancer. Barcelona Spain. 20(10 Supplement 1) (pp S864), 2025. Date of Publication: 01 Oct 2025.
Abstract:
Introduction: Pulmonary Langerhans cell histiocytosis (PLCH) is a rare, smoking-related neoplastic lung disease arising from clonal proliferation of dendritic cells. Initially considered a reactive disorder, the discovery of recurrent BRAF V600E mutations has led to its reclassification as a neoplasm. PLCH typically presents with nonspecific respiratory symptoms or may be incidentally detected on imaging. Diagnosis is based on high-resolution computed tomography, with histologic confirmation via biopsy. Smoking cessation remains the cornerstone of treatment, although glucocorticoids and BRAF-targeted therapies are used in selected cases. This study aims to characterize the incidence trends and survival outcomes of PLCH using a large population-based dataset in the U.S. Method(s): We performed a retrospective analysis using SEER (Surveillance, Epidemiology, and End Results) Research Plus (17 registries, 2010-2021). Patients with histologically confirmed Langerhans cell histiocytosis (ICD code 9751/ 3) with a primary site in the lung (C34) were included. Demographic and clinical data collected included age at diagnosis, sex, race/ ethnicity, stage at presentation, treatment modality, and county of residence (metropolitan vs. non-metropolitan). Incidence rates (IRs) per 100,000 were calculated using SEER*Stat and age-adjusted to the 2000 U.S. standard population. Kaplan-Meier survival analysis was performed using GraphPad Prism to evaluate overall survival (OS) and cancer-specific survival (CSS). Result(s): A total of 253 patients with PLCH were identified. The cohort was 57% female and 43% male, with 73% White, 15% Black, 6% Hispanic, 3.5% Asian/Pacific Islander, and 1% American Indian/Alaska Native. At diagnosis, 73% had localized disease and 20% presented with metastases. The overall age-adjusted IR was 0.0132 per 100,000, with the highest annual IR observed in 2016 (0.0493), followed by a decline. Females had a 33% higher IR than males (0.01509 vs. 0.01138; p = 0.028). While Black patients had a higher incidence (0.0190) compared to White patients (0.0160), the difference was not statistically significant (p = 0.37). The highest IR was observed in the 55-59 age group (IR = 0.03840), which was significantly higher than in the 40-44 (IR = 0.01419; p = 0.0004) and 35-39 (IR = 0.01261; p = 0.0001) groups, though not significantly different from those aged 45-54. Nonmetropolitan counties had a significantly higher IR (0.02507) compared to metropolitan counties (0.01185; p = 0.0004). The 5- and 10-year OS rates were 84.38% and 60.08%, respectively, while CSS rates were 96.25% and 93.39%. Adults aged >=60 years had a significantly shorter median OS (mOS) of 81 months compared to younger patients (p < 0.0001; HR 4.19, 95% CI 2.20-7.99). Conclusion(s): PLCH is an extremely rare pulmonary neoplasm with excellent cancer-specific survival but modest overall outcomes, likely reflecting comorbidities or delayed diagnosis. Incidence was highest in females, adults aged 55-59, and residents of nonmetropolitan areas, suggesting demographic and geographic disparities. These findings highlight the importance of early diagnosis and smoking cessation. The potential for disease stabilization or regression following smoking cessation differentiates PLCH from other lung neoplasms and underscores the need for timely recognition and intervention. Further investigation is warranted into the molecular framework and development of targeted therapies for this rare disease.
DOI: 10.1016/j.jtho.2025.09.1675
