The authors present long-term follow-up data on patients treated with Gamma Knife radiosurgery (GKRS) for acoustic neuroma.
Six hundred eighteen patients were radiosurgically treated for acoustic neuroma between 1992 and 2016 at the Department of Neurosurgery, Medical University Vienna. Patients with neurofibromatosis and patients treated too recently to attain 1 year of follow-up were excluded from this retrospective study. Thus, data on 557 patients with spontaneous acoustic neuroma of any Koos grade are presented, as are long-term follow-up data on 426 patients with a minimum follow-up of 2 years. Patients were assessed according to the Gardner-Robertson (GR) hearing scale and the House-Brackmann facial nerve function scale, both prior to GKRS and at the times of follow-up.
Four hundred fifty-two patients (81%) were treated with radiosurgery alone and 105 patients (19%) with combined microsurgery-radiosurgery. While the combined treatment was especially favored before 2002, the percentage of cases treated with radiosurgery alone has significantly increased since then. The overall complication rate after GKRS was low and has declined significantly in the last decade. The risk of developing hydrocephalus after GKRS increased with tumor size. One case (0.2%) of malignant transformation after GKRS was diagnosed. Radiological tumor control rates of 92%, 91%, and 91% at 5, 10, and 15 years after GKRS, regardless of the Koos grade or pretreatment, were observed. The overall tumor control rate without the need for additional treatment was even higher at 98%. At the last follow-up, functional hearing was preserved in 55% of patients who had been classified with GR hearing class I or II prior to GKRS. Hearing preservation rates of 53%, 34%, and 34% at 5, 10, and 15 years after GKRS were observed. The multivariate regression model revealed that the GR hearing class prior to GKRS and the median dose to the cochlea were independent predictors of the GR class at follow-up.
In small to medium-sized spontaneous acoustic neuromas, radiosurgery should be recognized as the primary treatment at an early stage. Although minimizing the cochlear dose seems beneficial for hearing preservation, the authors, like others before, do not recommend undertreating intracanalicular tumors in favor of low cochlear doses. For larger acoustic neuromas, radiosurgery remains a reliable management option with tumor control rates similar to those for smaller acoustic neuromas; however, careful patient selection and counseling are recommended given the higher risk of side effects. Microsurgery must be considered in acoustic neuromas with significant brainstem compression or hydrocephalus.
AkpinarBMousaviSHMcDowellMMNiranjanAFarajiAHFlickingerJC: Early radiosurgery improves hearing preservation in vestibular schwannoma patients with normal hearing at the time of diagnosis. Int J Radiat Oncol Biol Phys95:729–7342016
BailoMBoariNFranzinAGagliardiFSpinaADel VecchioA: Gamma Knife radiosurgery as primary treatment for large vestibular schwannomas: clinical results at long-term follow-up in a series of 59 patients. World Neurosurg95:487–5012016
BoariNBailoMGagliardiFFranzinAGemmaMdel VecchioA: Gamma Knife radiosurgery for vestibular schwannoma: clinical results at long-term follow-up in a series of 379 patients. J Neurosurg121Suppl:123–1422014
CarlsonMLHabermannEBWagieAEDriscollCLVan GompelJJJacobJT: The changing landscape of vestibular schwannoma management in the United States—a shift toward conservatism. Otolaryngol Head Neck Surg153:440–4462015
CarlsonMLTveitenOVDriscollCLGoplenFKNeffBAPollockBE: Long-term quality of life in patients with vestibular schwannoma: an international multicenter cross-sectional study comparing microsurgery, stereotactic radiosurgery, observation, and nontumor controls. J Neurosurg122:833–8422015
HasegawaTKidaYKatoTIizukaHKuramitsuSYamamotoT: Long-term safety and efficacy of stereotactic radiosurgery for vestibular schwannomas: evaluation of 440 patients more than 10 years after treatment with Gamma Knife surgery. J Neurosurg118:557–5652013
JacobJTCarlsonMLSchieferTKPollockBEDriscollCLLinkMJ: Significance of cochlear dose in the radiosurgical treatment of vestibular schwannoma: controversies and unanswered questions. Neurosurgery74:466–4742014
MarstonAPJacobJTCarlsonMLPollockBEDriscollCLWLinkMJ: Pretreatment growth rate as a predictor of tumor control following Gamma Knife radiosurgery for sporadic vestibular schwannoma. J Neurosurg127:380–3872017
McClellandSIIIGuoHOkuyemiKS: Morbidity and mortality following acoustic neuroma excision in the United States: analysis of racial disparities during a decade in the radiosurgery era. Neuro Oncol13:1252–12592011
RégisJCarronRParkMCSoumareODelsantiCThomassinJM: Wait-and-see strategy compared with proactive Gamma Knife surgery in patients with intracanalicular vestibular schwannomas. J Neurosurg113Suppl:105–1112010
YamakamiIUchinoYKobayashiEYamauraA: Conservative management, gamma-knife radiosurgery, and microsurgery for acoustic neurinomas: a systematic review of outcome and risk of three therapeutic options. Neurol Res25:682–6902003