Long‐term efficacy and safety of 2CdA (cladribine) in extra‐pulmonary adult‐onset Langerhans cell histiocytosis: analysis of 23 cases from the French Histiocytosis Group and systematic literature review

Langerhans cell histiocytosis (LCH) is a rare protean disease that usually affects children. Few data are available for management of adult-onset cases. A complete picture of the efficacy and safety of 2CdA (2-chlorodeoxyadenosine, cladribine) is lacking. We report a retrospective multicentre study of 23 adult LCH (a-LCH) patients who received single-agent 2CdA and a systematic literature review. All had previously received systemic therapy (vinblastine, n = 19). Response to 2CdA was evaluable in 22 cases. Overall response rate (ORR) was 91%. Complete response (CR) occurred in 11 cases (50%). Nine patients (39%) developed grade 3-4 neutropenia and/or severe infection. A literature review yielded 48 additional cases. A pooled analysis confirmed our findings (ORR: 88%, CR: 49%). CRs were rare with cumulative dose