Vinblastine/Prednisone Versus Single Therapy With Cytarabine for Langerhans Cell Histiocytosis (LCH)

Cytarabine 100 mg/m\^2/day IV for five consecutive days. This five-day cycle will be repeated every 21 days for a total of four cycles for all patients regardless of response. Each new cycle may not begin until absolute neutrophil count (ANC) is ≥ 750/mcL and platelet count is ≥ 75,000/mcL.

"Vinblastine/Prednisone +/- 6-mercaptopurine based on risk category. Patients with high-risk organ involvement (liver, spleen, hematopoeitic system) will receive 6-mercaptopurine during Continuation Therapy as this is the current standard of care treatment.~Vinblastine 6 mg/m\^2/dose IV push weekly for patients ≥ 12 months of age. Vinblastine will be dosed at 3 mg/m\^2/dose for patients under 6 months of age, and dosed at 4.5 mg/m\^2/dose for patients 6 months of age to 11.99 months of age.~Prednisone (or prednisolone) 20 mg/m2/dose by mouth twice a day"