Gamma Knife radiosurgery for vestibular schwannomas: evaluation of tumor control and its predictors in a large patient cohort in The Netherlands

Abstract

OBJECT The authors of this study sought to assess tumor control and complication rates in a large cohort of patients who underwent Gamma Knife radiosurgery (GKRS) for vestibular schwannoma (VS) and to identify predictors of tumor control. METHODS The records of 420 patients treated with GKRS for VS with a median marginal dose of 11 Gy were retrospectively analyzed. Patients with neurofibromatosis Type 2 or who had undergone treatment for VS previously were excluded. The authors assessed tumor control and complication rates with chart review and used the Cox proportional hazards model to identify predictors of tumor control. Preservation of serviceable hearing, defined as Gardner-Robertson Class I–II, was evaluated in a subgroup of 71 patients with serviceable hearing at baseline and with available follow-up audiograms. RESULTS The median VS tumor volume was 1.4 cm3, and the median length of follow-up was 5.1 years. Actuarial 5-and 10-year tumor control rates were 91.3% and 84.8%, respectively. Only tumor volume was a statistically significant predictor of tumor control rate. The tumor control rate decreased from 94.1% for tumors smaller than 0.5 cm3 to 80.7% for tumors larger than 6 cm3. Thirteen patients (3.1%) had new or increased permanent trigeminal nerve neuropathy, 4 (1.0%) had new or increased permanent facial weakness, and 5 (1.2%) exhibited new or increased hydrocephalus requiring a shunting procedure. Actuarial 3-year and 5-year hearing preservation rates were 65% and 42%, respectively. CONCLUSIONS The 5-year actuarial tumor control rate of 91.3% in this cohort of patients with VS compared slightly unfavorably with the rates reported in other large studies, but the complication and hearing preservation rates in this study were similar to those reported previously. Various factors may contribute to the observed differences in reported outcomes. These factors include variations in treatment indication and in the definition of treatment failure, as well as a lack of standardization of terminology and of evaluation of complications. Last, differences in dosimetric variables may also be an explanatory factor.

Gamma Knife radiosurgery for treatment of growing vestibular schwannomas in patients with neurofibromatosis Type 2: a matched cohort study with sporadic vestibular schwannomas

“…34 The difference between mutation types and therefore the proportion of both phenotypes might explain the difference in outcome of GKRS reported in the various published series. The view that a larger tumor volume is an independent factor associated with shortened PFS is supported by multivariate analysis done by Klijn et al 14…”

“…15 Current available studies on Gamma Knife radiosurgery (GKRS) for sporadic VS are abundant and show excellent results for tumor control and adverse effects. 14,16,21,25 For NF2-related VS, the number of studies is limited, and the studies show varying tumor control rates. 17,18,20,24,29,30,35,36 Consequently, the use of radiosurgery as a first-line treatment option is controversial.…”

Acute clinical adverse radiation effects after Gamma Knife surgery for vestibular schwannomas

“…Vertigo or gait disturbance was reported in up to 1.1% of patients, with a higher prevalence in the lower dose cohort, which also applied to tinnitus (occurring in 0.1%). In another recent study that provided data over a large cohort of 420 cases that were treated by GKS in the Netherlands, 9 the authors reported that 1% of patients had new or increased permanent facial weakness, 3.1% of patients reported trigeminal neuropathy, 1.2% of patients had new or increased hydrocephalus, up to 13.2% of patients reported tinnitus, and 14.8% of patients reported new or increased vertigo. In the same study, serviceable hearing was preserved in 60.6% of cases.…”

Therapy of Sporadic and NF2-Related Vestibular Schwannoma

“…Therefore, it is important VS are hypo-to isointense or isointense when compared to brain parenchyma on T1-weighted images [54][55][56]. Tumoral cysts are hypointense in comparison to the brain parenchyma on T1-weighted images [54,57]. The T1-weighted images can visualize intratumoral hemorrhage as an isointense or hyperintense area [58,59].…”