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

Clinical article

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Object

Little is known about long-term outcomes, including tumor control and adverse radiation effects, in patients harboring vestibular schwannomas (VSs) treated with stereotactic radiosurgery > 10 years previously. The aim of this study was to confirm whether Gamma Knife surgery (GKS) for VSs continues to be safe and effective > 10 years after treatment.

Methods

A total of 440 patients with VS (including neurofibromatosis Type 2) treated with GKS between May 1991 and December 2000 were evaluable. Of these, 347 patients (79%) underwent GKS as an initial treatment and 93 (21%) had undergone prior resection. Three hundred fifty-eight patients (81%) had a solid tumor and 82 (19%) had a cystic tumor. The median tumor volume was 2.8 cm3 and the median marginal dose was 12.8 Gy.

Results

The median follow-up period was 12.5 years. The actuarial 5- and ≥ 10-year progression-free survival was 93% and 92%, respectively. No patient developed treatment failure > 10 years after treatment. According to multivariate analysis, significant factors related to worse progression-free survival included brainstem compression with a deviation of the fourth ventricle (p < 0.0001), marginal dose ≤ 13 Gy (p = 0.01), prior treatment (p = 0.02), and female sex (p = 0.02). Of 287 patients treated at a recent optimum dose of ≤ 13 Gy, 3 (1%) developed facial palsy, including 2 with transient palsy and 1 with persistent palsy after a second GKS, and 3 (1%) developed facial numbness, including 2 with transient and 1 with persistent facial numbness. The actuarial 10-year facial nerve preservation rate was 97% in the high marginal dose group (> 13 Gy) and 100% in the low marginal dose group (≤ 13 Gy). Ten patients (2.3%) developed delayed cyst formation. One patient alone developed malignant transformation, indicating an incidence of 0.3%.

Conclusions

In this study GKS was a safe and effective treatment for the majority of patients followed > 10 years after treatment. Special attention should be paid to cyst formation and malignant transformation as late adverse radiation effects, although they appeared to be rare. However, it is necessary to collect further long-term follow-up data before making conclusions about the long-term safety and efficacy of GKS, especially for young patients with VSs.

Abbreviations used in this paper:GKS = Gamma Knife surgery; GR = Gardner-Robertson; HB = House-Brackmann; NF2 = neurofibromatosis Type 2; PFS = progression-free survival; SRS = stereotactic radiosurgery; VS = vestibular schwannoma.

Article Information

Address correspondence to: Toshinori Hasegawa, M.D., Department of Neurosurgery, Gamma Knife Center, Komaki City Hospital, 1-20 Jobushi, Komaki, Aichi Prefecture, 485-8520 Japan. email: h-toshi@komakihp.gr.jp.

Please include this information when citing this paper: published online November 9, 2012; DOI: 10.3171/2012.10.JNS12523.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Schematic drawings showing tumor classification depending on the location and brainstem compression. A: Type A—intracanalicular tumor. B: Type B—a cerebellopontine angle tumor without brainstem compression. C: Type C—tumor compressing the brainstem with no deviation of the fourth ventricle. D: Type D—tumor with a deviation of the fourth ventricle.

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    Kaplan-Meier curve demonstrating PFS in 427 patients in whom follow-up radiological studies were available.

  • View in gallery

    A comparison of Kaplan-Meier curves showing PFS between patients with Types A, B, or C and Type D tumors (upper), and between patients with tumors < 10 cm3 and ≥ 10 cm3 (lower).

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