Treatment Analysis and Overall Survival Outcomes of Patients With Bilateral Vestibular Schwannoma

Management of Central and Peripheral Nervous System Tumors in Patients with Neurofibromatosis

Neurofibromatosis type I (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis represent a diverse group of genetic tumor predisposition syndromes with a shared feature of tumors affecting the peripheral nerve sheaths. PURPOSE OF REVIEW: Many advancements have been made in understanding the biologic underpinnings of these conditions, and in 2016 the first drug was approved by the FDA to treat pediatric symptomatic unresectable plexiform neurofibromas. RECENT FINDINGS: Mek inhibitors have provided a much-needed therapeutic avenue for NF1 patients with unresectable plexiform neurofibromas (PN), both for reduction of tumor bulk and for improvement in symptoms. Selumetinib is the first FDA approved drug for PN, but is only approved for children. Some research suggests that alternative Mek inhibitors and other mixed tyrosine kinase inhibitors may have better efficacy in adults. Vascular endothelial growth factor (VEGF) inhibitor bevacizumab can prolong hearing and delay the need for surgery in NF2 patients with bilateral vestibular schwannomas. This article provides an update regarding considerations and approaches when treating the tumors associated with the neurofibromatoses (NF), including risk and prognosis metrics, clinical trial results, surgical techniques, and radiation therapy recommendations.

Long-term clinical outcomes of stereotactic radiotherapy for bilateral vestibular schwannomas in neurofibromatosis type 2 patients

PURPOSE

The evidence for treating patients with neurofibromatosis 2-related vestibular schwannoma (VS-NF2) using hypofractionated stereotactic radiation therapy (HSRT) is limited. This study aimed to investigate clinical outcomes in patients with VS-NF2 treated with Robotic HSRT.

METHODS

We retrospectively analyzed 25 NF2 patients with 48 VSs who were treated using Robotic HSRT at Ramathibodi Hospital from January 2009 to January 2020.

RESULTS

Median follow-up was 98 months (range, 24-155 months). Median tumor volume was 2.3 cm3 (range, 0.4-28.3 cm3). Median prescribed dose was 18 Gy (range, 18-25 Gy) in three fractions (range, 3-5). The 5- and 10-year local control rates were 87% and 80%, respectively. The 5- and 10-year hearing preservation rates were 59% and 35%, respectively. Three patients developed new symptoms associated with transient volume expansion after treatment: hydrocephalus in one, facial weakness in one, and ataxia in one. No patient developed worsening of trigeminal nerve function. No histologically confirmed of radiation induced malignancy was reported in the study.

CONCLUSIONS

Robotic HSRT demonstrated excellent long-term tumor control with a low non-auditory complication rate in patients with VS-NF2. However, preservation of hearing remains a major concern.

Vestibular schwannoma associated with neurofibromatosis type 2: Clinical course following stereotactic radiosurgery

Objective

A lack of understanding of the clinical course of neurofibromatosis type 2 (NF2)-associated vestibular schwannoma (VS) often complicates the decision-making in terms of optimal timing and mode of treatment. We investigated the outcomes of stereotactic radiosurgery (SRS) in this population.

Methods

We retrospectively analyzed NF2 patients treated with Gamma-Knife SRS for VS in our tertiary referral center. A total of 41 treated lesions from 33 patients were collected with a follow-up period of 69.1 (45.0-104.8) months. We reviewed the treatment history, hearing function, and other treatment-related morbidities in individual cases. We also analyzed pre- and post-treatment tumor volumes via imaging studies. Longitudinal volumetric analyses were conducted for the tumor volume response of the 41 treated lesions following SRS. The growth pattern of 22 unirradiated lesions during an observation period of 83.4 (61.1-120.4) months was separately evaluated.

Results

Most treated lesions showed effective tumor control up to 85% at 60 months after SRS, whereas unirradiated lesions progressed with a relative volume increase of 14.0% (7.8-27.0) per year during the observation period. Twelve (29%) cases showed pseudoprogression with significant volume expansion in the early follow-up period, which practically reduced the rate of tumor control to 57% at 24 months. Among the patients with serviceable hearing, two (20%) cases lost the hearing function on the treated side during the early follow-up period within 24 months.

Conclusions

Progressive NF2-associated VS can be adequately controlled by SRS but the short-term effects of this treatment are not highly advantageous in terms of preserving hearing function. SRS treatment candidates should therefore be carefully selected.

Stereotactic radiosurgery for vestibular schwannomas in neurofibromatosis type 2 patients: a systematic review and meta-analysis

INTRODUCTION

Neurofibromatosis type 2 (NF2) is characterized by often bilateral vestibular schwannomas (VS) that result in progressive hearing loss and compression of nearby brainstem structures causing cranial nerve palsies. Treatment of these tumors remains challenging, as both surgical removal and expectant management can result in symptom progression. Stereotactic radiosurgery (SRS) has been investigated for the management of NF2-associated VS; however, the role, promises, and pitfalls of this treatment modality remain unclear.

METHODS

Ovid MEDLINE, EMBASE, Web of Science, and Cochrane Reviews were searched for studies assessing SRS outcome in NF2-associated VS only. Primary endpoints included tumor control, serviceable hearing, presence of tinnitus, and cranial nerve V and VII symptoms.

RESULTS

A total of 16 studies (589 patients harboring 750 tumors) were analyzed. Clinical tumor control was achieved in 88% of cases (95% CI 80-95%); salvage surgery was needed in 8% (95% CI 4-13%) of cases. Treatment resulted in a worsening of pre-treatment serviceable hearing (OR = 0.26, p < 0.01), increased facial nerve (OR = 1.62, p < 0.01) and trigeminal nerve (OR = 1.42, p = 0.07) impairment. The incidence of vestibular symptoms and hydrocephalus were not consistently reported and thus could not be assessed.

CONCLUSIONS

The treatment of NF2-associated VS continues to pose a challenge, as current SRS regimens result in impaired hearing and worse cranial nerve comorbidities, despite achieving high tumor control. It remains unclear if these findings have to be regarded as treatment complications or, rather, continued disease progression.