Stereotactic Radiosurgery for Vestibular Schwannoma in Neurofibromatosis Type 2: An International Multicenter Case Series of Response and Malignant Transformation Risk

Othman Bin-Alamer, Andrew Faramand, Norah A. Alarifi, Zhishuo Wei, Arka N. Mallela, Victor M. Lu, Ahmed M. Nabeel, Wael A. Reda, Sameh R. Tawadros, Khaled Abdelkarim, Amr M.N. El-Shehaby, Reem M. Emad, Selcuk Peker, Yavuz Samanci, Cheng-chia Lee, Huai-che Yang, Violaine Delabar, David Mathieu, Manjul Tripathi, Kathryn Nicole Kearns, Adomas Bunevicius, Jason P. Sheehan, Tomas Chytka, Roman Liscak, Nuria Martínez Moreno, Roberto Martínez Álvarez, Inga S. Grills, Jacob S. Parzen, Christopher P. Cifarelli, Azeem A. Rehman, Herwin Speckter, Ajay Niranjan, L. Dade Lunsford, Hussam Abou-Al-Shaar

Vestibular schwannomas (VSs) related to neurofibromatosis type 2 (NF2) are challenging tumors. The increasing use of stereotactic radiosurgery (SRS) necessitates further investigations of its role and safety. To evaluate tumor control, freedom from additional treatment (FFAT), serviceable hearing preservation, and radiation-related risks of patients with NF2 after SRS for VS. We performed a retrospective study of 267 patients with NF2 (328 VSs) who underwent single-session SRS at 12 centers participating in the International Radiosurgery Research Foundation. The median patient age was 31 years (IQR, 21-45 years), and 52% were male. A total of 328 tumors underwent SRS during a median follow-up time of 59 months (IQR, 23-112 months). At 10 and 15 years, the tumor control rates were 77% (95% CI: 69%-84%) and 52% (95% CI: 40%-64%), respectively, and the FFAT rate were 85% (95% CI: 79%-90%) and 75% (95% CI: 65%-86%), respectively. At 5 and 10 years, the serviceable hearing preservation rates were 64% (95% CI: 55%-75%) and 35% (95% CI: 25%-54%), respectively. In the multivariate analysis, age (hazards ratio: 1.03 [95% CI: 1.01-1.05]; P = .02) and bilateral VSs (hazards ratio: 4.56 [95% CI: 1.05-19.78]; P = .04) were predictors for serviceable hearing loss. Neither radiation-induced tumors nor malignant transformation were encountered in this cohort. Although the absolute volumetric tumor progression rate was 48% at 15 years, the rate of FFAT related to VS was 75% at 15 years after SRS. None of the patients with NF2-related VS developed a new radiation-related neoplasm or malignant transformation after SRS.