Proton Radiotherapy for Vestibular Schwannomas in Patients with NF2-Related Schwannomatosis: A Case Series

SIMPLE SUMMARY: The management of vestibular schwannomas in neurofibromatosis type 2-related schwannomatosis (NF2) is complex. Current treatment strategies include active surveillance, surgery, radiotherapy, and pharmacotherapy. Due to treatment side effects such as hearing loss, balance complaints, or cranial nerve deficits, it remains challenging to find a treatment that achieves a good control of tumor growth with minimal side effects. The present study found that the majority of NF2 patients was treated with proton radiotherapy as salvage treatment for vestibular schwannoma and did not require additional interventions. However, they did experience significant tumor and/or treatment-related side effects. The value of proton radiotherapy as a primary treatment for vestibular schwannomas in NF2 patients remains to be determined. ABSTRACT: (1) Background: This study aimed to evaluate the efficacy and treatment-related toxicity of proton radiotherapy (PRT) for vestibular schwannoma (VS) in patients with neurofibromatosis type 2-related schwannomatosis (NF2). (2) Methods: Consecutive NF2 patients treated with PRT for VS between 2004 and 2016 were retrospectively evaluated, focusing on tumor volume, facial and trigeminal nerve function, hearing, tinnitus, vestibular symptoms, and the need for salvage therapy after PRT. (3) Results: Eight patients were included (median age 36 years, 50% female). Median follow-up was 71 months. Five (63%) patients received fractionated PRT and three (38%) received PRT radiosurgery for VS. Six patients (75%) received prior VS surgery; three also received bevacizumab. Six patients (75%) did not require salvage therapy after PRT. Two patients (25%) with residual hearing lost it after PRT, and six had already lost ipsilateral hearing prior to PRT. Tumor and treatment-related morbidity could be evaluated in six patients. Following PRT, conditions that occurred or worsened were: facial paresis in five (83%), trigeminal hypoesthesia in two (33%), tinnitus in two (33%), and vestibular symptoms in four patients (67%). (4) Conclusion: After PRT for VS, the majority of the NF2 patients in the cohort did not require additional therapy. Tumor and/or treatment-related cranial nerve deficits were common. This is at least partly explained by the use of PRT as a salvage treatment after surgery or bevacizumab, in the majority of cases. There remains the further opportunity to elucidate the efficacy and toxicity of proton radiotherapy as a primary treatment.