Case report: Successful use of MEK inhibitors as an adjuvant approach in the treatment of pediatric MAP4-RAF1 fusion-positive solid tumor.

RAF protein kinase acts downstream of RAS in the MAPK pathway, and mutations in the RAF family protein BRAF are frequently observed in adult tumours, with MEK inhibitors proving effective in treatment. However, RAF family protein RAF1 fusions are rare, particularly in pediatric soft tissue tumors, and the efficacy of targeted therapies remains uncertain. This study presents a rare case of a MAP4-RAF1 fusion-positive solid tumor in a child, unresponsive to conventional chemotherapy, surgery, second-line chemotherapy, and sorafenib-targeted therapy. Protein structure simulations predicted trametinib to exhibit optimal efficacy among MEK inhibitors in structural modelling, and it then demonstrated clinical effectiveness in this child. This study underscores the importance of molecular interaction simulations in precise drug screening for clinical decision-making and highlights MEK inhibitors' potential as adjunctive therapy for pediatric RAF1 fusion tumors.