Intermediate-dose cytarabine is an effective therapy for adults with non-Langerhans cell histiocytosis

Background Non-Langerhans cell histiocytosis, including Erdheim–Chester disease (ECD), Rosai–Dorfman disease (RDD), indeterminate cell histiocytosis (ICH), and unclassified histiocytosis, is a rare disorder lacking a standard treatment strategy. We report our experience using intermediate-dose cytarabine as the first or subsequent therapy in non-Langerhans cell histiocytosis. Results Eight ECD patients, 5 RDD patients, 1 ICH patient and 1 unclassified histiocytosis patient were enrolled. Intermediate-dose cytarabine therapy was administered as 0.5-1.0 mg/m2 of intravenous cytarabine every 12 hours for 3 days every 5 weeks. The median age at cytarabine initiation was 45 years (range, 18–70 years). The median number of cycles of cytarabine administered was 6 (range, 2–6). The overall response rate (ORR) was 86.7% in the overall cohort, including 6.7% with complete response and 80.0% with partial response. All patients (n=10) with CNS involvement achieved disease improvements. One patient experienced disease recurrence 19 months after cytarabine therapy. The median follow-up duration for the entire cohort was 12 months (range, 4-61 months). The 1-year progression-free survival (PFS) and overall survival (OS) rates were 85.6% and 92.3%, respectively. The most common toxicity was haematological adverse events, including grade 4 neutropenia and grade 3-4 thrombocytopenia. No treatment-related deaths occurred. Conclusions Intermediate-dose cytarabine is a cost-effective treatment option for non-Langerhans cell histiocytosis patients, especially for those with CNS involvement.