Stereotactic radiosurgery for vestibular schwannomas: average 10-year follow-up results focusing on long-term hearing preservation

Abstract

OBJECTIVEThe aim of this study was to reappraise long-term treatment outcomes of stereotactic radiosurgery (SRS) for vestibular schwannomas (VSs). The authors used a database that included patients who underwent SRS with a unique dose-planning technique, i.e., partial tumor coverage designed to avoid excess irradiation of the facial and cochlear nerves, focusing on tumor control and hearing preservation. Clinical factors associated with post-SRS tumor control and long-term hearing preservation were also analyzed.METHODSThis institutional review board–approved, retrospective cohort study used the authors' prospectively accumulated database. Among 207 patients who underwent Gamma Knife SRS for VSs between 1990 and 2005, 183 (who were followed up for at least 36 post-SRS months) were studied. The median tumor volume was 2.0 cm3 (range 0.05–26.2 cm3). The median prescribed dose at the tumor periphery was 12.0 Gy (range 8.8–15.0 Gy; 12.0 Gy was used in 171 patients [93%]), whereas tumor portions facing the facial and cochlear nerves were irradiated with 10.0 Gy. As a result, 72%–99% of each tumor was irradiated with the prescribed dose. The mean cochlear doses ranged from 2.3 to 5.7 Gy (median 4.1 Gy).RESULTSThe median durations of imaging and audiometric follow-up were 114 months (interquartile range 73–144 months) and 59 months (interquartile range 33–109 months), respectively. Tumor shrinkage was documented in 110 (61%), no change in 48 (27%), and enlargement in the other 22 (12%) patients. A further procedure (FP) was required in 15 (8%) patients. Thus, the tumor growth control rate was 88% and the clinical control rate (i.e., no need for an FP) was 92%. The cumulative FP-free rates were 96%, 93%, and 87% at the 60th, 120th, and 180th post-SRS month, respectively. Six (3%) patients experienced facial pain, and 2 developed transient facial palsy. Serviceable hearing was defined as a pure tone audiogram result better than 50 dB. Among the 66 patients with serviceable hearing before SRS who were followed up, hearing acuity was preserved in 23 (35%). Actuarial serviceable hearing preservation rates were 49%, 24%, and 12% at the 60th, 120th, and 180th post-SRS month, respectively. On univariable analysis, only cystic-type tumor (HR 3.36, 95% CI 1.18–9.36; p = 0.02) was shown to have a significantly unfavorable association with FP. Multivariable analysis followed by univariable analysis revealed that higher age (≥ 65 years: HR 2.66, 95% CI 1.16–5.92; p = 0.02), larger tumor volume (≥ 8 cm3: HR 5.36, 95% CI 1.20–17.4; p = 0.03), and higher cochlear dose (mean cochlear dose > 4.2 Gy: HR 2.22, 95% CI 1.07–4.77; p = 0.03) were unfavorable factors for hearing preservation.CONCLUSIONSStereotactic radiosurgery achieved good long-term results in this series. Tumor control was acceptable, and there were few serious complications in patients with small- to medium-sized VSs. Unfortunately, hearing preservation was not satisfactory. However, the longer the observation period, the more important it becomes to compare post-SRS hearing decreases with the natural decline in untreated cases.

Hearing preservation after Gamma Knife radiosurgery for cerebellopontine angle meningiomas

“…10,17,18,25,26,33,37,43 Several factors have been suggested to affect hearing preservation, including tumor volume, pretreatment hearing status, age, cochlear dose, brainstem cochlear nucleus dose, and marginal dose ≤ 13 Gy. 8,9,11,21,26,33,38,43,46 Similarly, we found that patients with Grade I hearing fared better regarding hearing preservation. This was clearly evident when we compared these patients with those with Grade II hearing.…”

“…The incidence of CPA meningiomas with serviceable hearing on presentation is reported to be 39%-88%. 23,34,35,46 In the current study the incidence was 27%. The wide incidence variability is probably related to the location criteria, as the CPA location is a wide space located between the lateral cerebellum and pons.…”

“…The hearing preservation rate after surgery for CPA meningiomas is reported to be 60%-100%. 1,2,12,46 Some studies reported on the hearing preservation rate after surgery for meningiomas extending into the IAC, which was not as good, ranging from 15% to 71%. 4,7,15,24,27,28,31,35,41,48 The location of the meningiomas within the CPA was found to influence hearing outcome.…”

Clinical Results After Single-fraction Radiosurgery for 1,002 Vestibular Schwannomas

“…However, long-term data with reasonably large patient cohorts are missing and few quality-of-life evaluations after SRS for VS have been presented to date [1][2]. Moreover, most published series comprise smaller heterogeneous patient groups treated with inconsistent radiosurgical techniques and doses [3][4][5]. While there has been a tendency to treat increasingly smaller and sometimes asymptomatic tumors, concerns have been raised regarding long-term hearing toxicity and cases of suspected malignant transformation [6][7].…”

Three-stage Gamma Knife treatment for metastatic brain tumors larger than 10 cm3: a 2-institute study including re-analyses of earlier results using competing risk analysis

“…Our above-mentioned criteria for neurological death, neurological deterioration, local recurrence, and complications have been widely confirmed based on our previous publications. 14,[31][32][33][34][35][36]38…”