Targeted therapy for Langerhans cell histiocytosis with maxillofacial involvement in 20 children

To evaluate targeted therapy for Langerhans cell histiocytosis (LCH) with maxillofacial manifestations, we conducted a retrospective study of 20 children admitted from January 2016 to June 2021.

The maxillofacial LCH exhibited diverse clinical features and laboratory indices. Seventeen patients were refractory to standard treatments, and three patients directly underwent targeted therapy. Sixteen patients with BRAF^V600E mutation were treated with dabrafenib, and four patients with MAP2K1 mutation were treated with trametinib.

The cohort included nine males and eleven females, with a median 0.92 years at diagnosis and 1.70 years at initiation of targeted therapy. Three patients had single-system LCH and 17 patients had multi-system LCH. Lesions affected the mandibular bone in 17 patients, the temporal bone in 12 patients, and the maxilla in 10 patients. Ki-67 expression before targeted therapy correlates with maxillary involvement (coefficient 0.61; P < 0.05). The cfBRAF^V600E level after first month of targeted therapy was significantly lower than before targeted therapy (P < 0.001). After a median 18 months of targeted therapy and 22 months of follow-up, 17 patients achieved complete remission, and 3 patients achieved partial remission. The objective response rate was 65%, and the disease control rate was 100%. Five patients experienced progression or reactivation, and ten patients had skin rashes.

Overall, targeted therapy demonstrated good efficacy with mild tolerable adverse events.