NFS-30. ADJUVANT MEK INHIBITION TO PREVENT REBOUND GROWTH FOLLOWING PARTIAL RESECTION OF PLEXIFORM NEUROFIBROMAS

Abstract

Abstract BACKGROUND Plexiform neurofibromas (PNs) are benign peripheral nerve sheath tumors that occur in patients with neurofibromatosis type I. These tumors can cause significant morbidity leading to functional impairment, pain, and disfigurement. Management of PNs is challenging. Complete surgical resection is often not possible due to tumor growth along vital structures, and rebound growth is frequently experienced following subtotal resection (STR) of PNs. The mitogen-activated protein kinase (MAPK) pathway has been implicated in the growth of PNs, and the use of MAPK enzyme (MEK1/2) inhibitors has been shown to be an effective therapy in the treatment of PNs. Herein, we described our institutional experience using a short course of adjuvant MEK1/2 inhibitors in the treatment of pediatric patients with PNs following STR to prevent rebound growth. METHODS A single-institution retrospective record review of pediatric patients who underwent STR of their PN. RESULTS A total of 35 patients with 39 separate PNs had STR of their PNs. Fourteen PNs were treated with resection alone and 25 PNs were treated with a six-month course of adjuvant MEK1/2 inhibitors following STR. The number of patients requiring additional treatment with surgical resection or medical therapy was 11 of 14 patients (79%) in the resection only group and 6 of 25 patients (24%) in the adjuvant MEK1/2 inhibitor group. The mean time to additional treatment for the resection only group was 22 months, and the mean follow-up time for patients receiving adjuvant MEK1/2 inhibition was 29 months. Skin rash was the most common adverse effect seen with adjuvant MEK1/2 inhibition, and one patient experienced a dose-limiting thrombus. CONCLUSIONS A short course of MEK1/2 inhibitors following STR of PNs is effective in the short-term in preventing rebound growth when compared to STR alone. Treatment is well tolerated and should be considered as adjuvant therapy in pediatric patients.