Hematopoietic stem cell transplantation for Langerhans cell histiocytosis: clinical findings and long-term outcomes

ABSTRACT

Introduction

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by accumulation of bone marrow-derived immature dendritic cells harboring oncogenic mutations in mitogen-activated protein kinase (MAPK) pathway genes, such as BRAF^V600E, and various reactive inflammatory cells. Infants with chemo-resistant multisystem disease with risk organ involvement [MS-RO(+)] have poor prognosis. Further, relapsed infants have a significant risk of developing disastrous neuro-degenerative central nervous system disease.

Areas covered

This review covers published papers on hematopoietic stem cell transplantation (HSCT) for LCH selected through a literature search on PubMed between years 1985 and 2019.

Expert opinion: Infants with refractory MS-RO(+) disease or with frequent treatment-resistant relapses can benefit from allogeneic HSCT (allo-HSCT). Selection of an HLA-matched sibling or unrelated cord blood (UCB) stem cell source and use of reduced intensity conditioning (RIC) preparative regimens, based on the combination fludarabine with melphalan, are preferable. Most deaths after HSCT occur within 3 months, due to transplantation-related complications. LCH disease activity usually regresses over 3 months after allo-HSCT in survivors. The disease activity at HSCT is the most important prognostic factor. Prior to HSCT, the disease activity should be reduced by treatment.

KEYWORDS:

• BRAF V600E mutation
• cord blood cell transplantation
• fludarabine
• mitogen-activated protein kinase
• melphalan
• reduced intensity conditioning
• risk organ involvement

Article highlights

• Infants with refractory MS-RO(+) LCH, or LCH with frequent treatment-resistant relapse, can benefit from allo-HSCT.

• HLA-matched sibling or UCB are preferable stem cell sources.

• RIC, based on the combination of Flu and MEL, should be selected for the preparative regimen.

• Most deaths after HSCT occur within 3 months due to TRC; in survivors, disease activity usually regresses over 3 months after allo-HSCT.

• Disease activity at HSCT is the most important prognostic factor.

• Until long-term treatment with MAPK inhibitors has been established and standardized, early allo-HSCT with a RIC regimen using UCB, after reduction of disease activity using CSs and BRAF inhibitors, may be standard therapy for infants with refractory MS-RO(+) LCH.

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Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was funded by the Ministry of Education, Culture, Sports, Science and Technology, Japan, [#18K07828].