Cytarabine-based induction and oral maintenance therapy for a single system with single-site Langerhans cell histiocytosis.

Single-system, single-site (SS-s) Langerhans cell histiocytosis (LCH) is usually managed with observation or local therapy; however, a subset of patients requires systemic chemotherapy, although the optimal intensity for this group remains unclear. In this study, we retrospectively reviewed patients with newly diagnosed or recurrent SS-s LCH who were treated at our institution. They received 6 weeks of induction chemotherapy with cytarabine, vincristine, and prednisolone, followed by 1 year of oral maintenance therapy with 6-mercaptopurine and methotrexate. Of these patients, 15 were evaluable (13 newly diagnosed and 2 recurrent). At the end of induction, all patients achieved a good or partial response and were administered maintenance therapy, after which they achieved a good response. With a median follow-up of 5.6 years, all patients were alive without subsequent relapse, death, or central nervous system (CNS) complications. No grade 3 or 4 nonhematologic toxicities were observed, except transient increases in liver enzymes during maintenance therapy. No adverse events occurred that required hospitalization. These results suggest that cytarabine-based induction followed by oral maintenance may be an effective and tolerable option for patients with SS-s LCH requiring systemic therapy.