Stereotactic radiosurgery as the primary management for patients with Koos grade IV vestibular schwannomas

Abstract

OBJECTIVEWhile extensive long-term outcome studies support the role of stereotactic radiosurgery (SRS) for smaller-volume vestibular schwannomas (VSs), its role in the management for larger-volume tumors remains controversial.METHODSBetween 1987 and 2017, the authors performed single-session SRS on 170 patients with previously untreated Koos grade IV VSs (volumes ranged from 5 to 20 cm3). The median tumor volume was 7.4 cm3. The median maximum extracanalicular tumor diameter was 27.5 mm. All tumors compressed the middle cerebellar peduncle and distorted the fourth ventricle. Ninety-three patients were male, 77 were female, and the median age was 61 years. Sixty-two patients had serviceable hearing (Gardner-Robertson [GR] grades I and II). The median margin dose was 12.5 Gy.RESULTSAt a median follow-up of 5.1 years, the progression-free survival rates of VSs treated with a margin dose ≥ 12.0 Gy were 98.4% at 3 years, 95.3% at 5 years, and 90.7% at 10 years. In contrast, the tumor control rate after delivery of a margin dose < 12.0 Gy was 76.9% at 3, 5, and 10 years. The hearing preservation rates in patients with serviceable hearing at the time of SRS were 58.1% at 3 years, 50.3% at 5 years, and 35.9% at 7 years. Younger age (< 60 years, p = 0.036) and initial GR grade I (p = 0.006) were associated with improved serviceable hearing preservation rate. Seven patients (4%) developed facial neuropathy during the follow-up interval. A smaller tumor volume (< 10 cm3, p = 0.002) and a lower margin dose (≤ 13.0 Gy, p < 0.001) were associated with preservation of facial nerve function. The probability of delayed facial neuropathy when the margin dose was ≤ 13.0 Gy was 1.1% at 10 years. Nine patients (5%) required a ventriculoperitoneal shunt because of delayed symptomatic hydrocephalus. Fifteen patients (9%) developed detectable trigeminal neuropathy. Delayed resection was performed in 4% of patients.CONCLUSIONSEven for larger-volume VSs, single-session SRS prevented the need for delayed resection in almost 90% at 10 years. For patients with minimal symptoms of tumor mass effect, SRS should be considered an effective alternative to surgery in most patients, especially those with advanced age or medical comorbidities.

Stereotactic radiosurgery for Koos grade IV vestibular schwannoma in young patients: a multi-institutional study

“…In this analysis of 176 patients, at a median follow-up of 37.5 (IQR 53.5) months, tumor control was 93.2%. The actuarial tumor control at 5-and 10-years was 90.9% and 86.7%, respectively in accordance to previously reported tumor control rates ranging from 88-97.9% [4,[22][23][24]. Early tumor expansion is the sole risk factor of tumor progression, p < 0.0001, HR:19.6 [CI95%5.…”

“…Serviceable hearing preservation after SRS in large VS was reported between 0-82% [4-7, 23, 24, 32-34] and is similar to the young cohort recently published [25]. Pre-SRS GR class I [4,35,36], central cochlear dose < 4.2 Gy [36], mean cochlear dose < 6 Gy [35], and age < 60 years old were factors associated with hearing preservation [4]. In our study, female gender was the only factor to be associated with serviceable hearing at last follow-up in multivariate analysis.…”

“…1-75.8]. In contrast to the study by Ogino et al [4], the margin dose in this report was not identi ed as a risk factor for tumor progression. A recent study from Kawashima et al, shows a tumor control at 5-and 10 years of 90.2% and 85.4% in 49 young patients with primary or secondary SRS.…”

“…Post-SRS facial nerve neuropathy was described between 0-4% in recent series for large vestibular schwannoma [4][5][6][7]23]. In the present study, worsening of facial nerve function was reported in 2.8% of the patients at last follow-up.…”

“…However, the management of patients with medical contraindications to or those who refuse surgery remains controversial. Literature reporting outcomes of SRS for Koos grade IV VS are limited mostly to single center series [4][5][6][7]. Recently, a multi-institutional, retrospective study was published showing good tumor control and facial nerve preservation, increasing the evidence for the effectiveness of SRS as an alternative to surgery in these cases [8].…”