Clinical outcomes and screening for organ involvement in pediatric Langerhans cell histiocytosis in Thailand: multicenter study on behalf of the Thai Pediatric Oncology Group.

Langerhans cell histiocytosis (LCH) is a rare disease across all age groups and is characterized by various degrees of severity and organ system involvement. A multi-institutional retrospective study of pediatric patients with LCH treated between 1999 and 2018 at five pediatric oncology centers was conducted to describe the clinical characteristics, prognostic factors, and outcomes of LCH and to validate screening tools for organ system involvement in pediatric LCH in Thailand. A total of 127 patients with a median age of 2.7 years were studied. The single-to-multisystem (MS) LCH ratio was 1:1. Forty-seven patients (71%) with MS-LCH had risk-organ involvement (RO +), whereas 19 (29%) patients had no risk-organ involvement (RO -). The 5-year overall and event-free survival rates were 91.3% and 73.6%, respectively, which were comparable to those in developed countries. Prognostic factors included age < 2 years, RO + MS-LCH, and number of RO + . Abnormal complete blood count was a highly sensitive indicator of bone marrow involvement. Plain radiography is an appropriate screening tool to detect bone involvement.