Pulmonary involvement in pediatric-onset multisystem Langerhans cell histiocytosis: effect on course and outcome

OBJECTIVES: To assess the effect of pulmonary involvement on the course and outcome of multisystem Langerhans cell histiocytosis (MS-LCH) in children.

STUDY DESIGN: We conducted a retrospective analysis of 420 consecutive patients with MS-LCH. In this analysis, the term "risk organs" is defined as involvement of the liver, spleen, and/or hematopoietic system. The effect of pulmonary involvement on survival was assessed with multivariate Cox regression with adjustment for risk organs involvement and age.

RESULTS: Pulmonary involvement in MS-LCH was present at diagnosis in 102 patients (24%). Of the 318 patients without pulmonary involvement at diagnosis, it developed in 28 within a median of 10 months (range, 1 month-5.5 years). The 5-year overall survival rate in patients without risk organ involvement at diagnosis was 96% in patients without pulmonary involvement and 94% in those with pulmonary involvement. In patients with risk organ involvement at diagnosis, the 5-year overall survival rate was 73% in patients without pulmonary involvement and 65% in patients with pulmonary involvement. In multivariate analysis, pulmonary involvement at diagnosis had no significant impact on survival rats (P = .109, hazard ratio = 1.5).

CONCLUSIONS: In multivariate analysis, pulmonary involvement was not an independent prognostic variable and should therefore be excluded from the definition of risk organ involvement in MS-LCH.