2.2 Therapeutic regimen
Based on the number of involved organs/systems, LCH was categorized into two types: single-system (SS-LCH) with unifocal or multifocal involvement and multi-system (MS-LCH) with two or more organs/systems involvements. MS-LCH was classified as risk organ (RO) positive (liver, spleen, and/or hematopoietic system) or negative according to LCH extent26.
Most of the enrolled patients received the standard first-line chemotherapy, based on the LCH-III protocols27-29. Briefly, the first-line therapy comprised one or two six-week courses of initial induction therapy (vindesine-steroid combination) and maintenance therapy (vindesine, prednisone, with or without 6-mercaptopurine). The overall duration of first-line treatment was 12 months or six months (for non-CNS-risk SS-LCH with good response to the first induction treatment). BRAF inhibitor dabrafenib was directly administered to those BRAF -V600E-mutated MS-LCH patients who were under two years old or unable to endure the standard chemotherapy30. Treatment response were assessed according to International LCH study Group criteria8,26.