What is JLSG?

Langerhans cell histiocytosis (LCH) occurs primarily in childhood and is a rare clonal disorder of Langerhans cell proliferation, which is one of the antigen presenting cells originated in bone marrow. LCH develops as unifocal or multifocal lesions at various sites, such as bone, skin, lymph nodes, liver/spleen, thymus, central nervous system (CNS). The multifocal LCH lesions occur as single-system multi-site (SS-m) or multi-system (MS) types.

A retrospective epidemiologic survey performed in Japan from 1986 to 1990 revealed that nearly 20% of the multifocal LCH patients died. These results clearly indicated the necessity of better clinical trials. With use of various institutional protocols, low induction and high reactivation rates occurring after the initial treatment were associated with poor prognosis of multifocal LCH. In addition, late sequelae such as diabetes insipidus (DI), orthopedic complications, CNS disorders or secondary leukemia associated with VP-16 also became major problems during or after systemic chemotherapy. However, the optimal drug treatment combination and the optimum length of the treatment for LCH have long remained to be determined.

To overcome these unfavorable and unsatisfactory treatment results in pediatric multifocal LCH, we established the Japan LCH study group (JLSG) in 1996 and conducted the prospective multicenter cooperative study with the protocol JLSG-96 from 1996 to 2002.

The JLSG-96 study confirmed that outcome of multifocal LCH can be improved by the treatment with multidrug intensified chemotherapy. We attained a significantly low mortality rate (5.1%) in Japan. Nevertheless, the low event free survival (＜40%) and high reactivation (nearly 50%) rates remained unsatisfactory.

To further improve the quality of life in multi-focal LCH patients, we have started a modified new treatment protocol (JLSG-02) from 2002 to date.