Clinical features and treatment outcomes of Langerhans cell histiocytosis: a nationwide survey from Korea histiocytosis working party.

A nationwide survey was conducted to clarify the clinical features and outcomes of Korean children with Langerhans cell histiocytosis (LCH). Korea Histiocytosis Working Party analyzed the data of 603 patients who were diagnosed with LCH between 1986 and 2010 from 28 institutions in Korea. Median age at diagnosis was 65 months (range, 0 to 276 mo). Bone was the most frequently affected organ (79.6%) followed by skin (19.2%). Initially, 419 patients (69.5%) had single-system involvement (SS), 85 (14.1%) with multisystem (MS) disease without risk organ involvement (MS-RO), and 99 (16.4%) multisystem disease with risk organ involvement (MS-RO). The 5-year overall survival (OS) rates in the SS, MS-RO, and MS-RO groups were 99.8%, 98.4%, and 77.0%, respectively (P<0.001), and the 5-year reactivation rates were 17.9%, 33.5%, and 34.3%, respectively (P<0.001). The OS rate was lower in patients with RO involvement (P=0.025) and lack of response to initial treatment (P=0.001). MS involvement (P=0.036) was an independent risk factor for reactivation. Permanent consequences were documented in 99 patients (16.4%). Reactivation of disease, MS involvement, and age at diagnosis ≤ 2 years were associated with higher incidence of permanent consequences. This study emphasized that further efforts are required to improve survival of MS-RO patients and reduce reactivation in younger patients with MS involvement.