Long-term outcome of gamma knife radiosurgery for vestibular schwannoma

A 25-Year Update on the Facial Nerve Sparing Approach for Vestibular Schwannoma

BACKGROUND

This study updates the results of a facial nerve preservation approach to treating vestibular schwannomas at a single institution by a single surgeon using retrosigmoid craniectomy with microsurgery (MS) and gamma knife stereotactic radiosurgery (SRS) over a 25-year interval.

METHODS

We retrospectively reviewed 751 patients between 1998 and 2023 and grouped them by intervention: MS only (Group 1, 217 patients), SRS only (Group 2, 447 patients), MS then SRS (Group 3, 72 patients), SRS then MS (Group 4, 10 patients), and SRS then SRS (Group 5, 5 patients). The primary outcome variable was facial nerve function, defined as House-Brackmann grade ≤2 at last follow-up.

RESULTS

Good outcomes by group were achieved in 98.2%, 99.6%, 93.1%, 90%, and 100% of patients, respectively. Upfront SRS (Group 2) resulted in significantly better facial nerve outcomes than upfront MS (Groups 1 and 3, 289 patients) (96.9% and 99.4%, P < 0.05). Mean tumor maximum linear diameters were 3.2, 1.32, 3.23, 1.98, and 1.64 cm. Subtotal resection rates in Groups 1, 3, and 4, were 68.2%, 81.9%, and 80%, respectively. The median (interquartile range) follow-up time among patients (minimum follow-up of 12 months) was 52 (26.75-88) months, with a maximum of 297 months (24.75 years). Overall, 98.1% of patients had a good facial nerve outcome with no operative mortality.

CONCLUSIONS

For larger tumors, MS emphasizing facial nerve preservation over gross total resection followed by adjuvant SRS for any interval tumor regrowth yields excellent facial nerve outcomes and tumor control rates. For smaller tumors, upfront SRS achieves superior facial nerve preservation with MS and SRS both viable salvage options for treatment of tumor progression. This paradigm balances tumor control, facial nerve preservation, and low morbidity.

Risk analysis of radiosurgery for vestibular schwannoma: Systematic review and comparative study of 10-year outcomes

Background

Determine the benefit of stereotactic radiosurgery (SRS) compared to no treatment for sporadic vestibular schwannoma (VS) by calculating epidemiologic risk using 10-year data; apply the analysis to VS that have demonstrated linear growth.

Methods

PubMed, Google Scholar, Web of Science, and Cochrane Library are systematically reviewed for VS tumor control 10 years after SRS and compared to a historical cohort of untreated VS (primary risk analysis). Subgroups of VS limited by size and observed growth are compared to the untreated cohort (secondary analysis).

Results

Twenty-four studies of 4079 SRS-treated VS exhibited tumor control in 90.93% (87.0%-100%; SD 4.1%), while 1959 untreated VS exhibited control in 65.24%. SRS reduces the absolute risk (ARR) of tumor progression by 25.7% compared to no treatment. The number needed to treat (NNT) is 4 (3.892, 95% CI: 3.619-4.210). Subgroup analyses of (1) VS with definite linear growth before SRS result in a similar ARR of 29.4% and NNT 4 (3.395, 95% CI: 2.966-3.968), and (2) Koos 1 VS result in lower ARR 18.31% and higher NNT 6 (5.209; 95% CI: 4.018-7.401).

Conclusions

This "best-available" case-control study of 10-year data reveals that ARR and NNT are similar for VS with and without definite pretreatment linear growth. These comparisons may be applied to CPA diameters less than 2 cm. Results for Koos 1 tumors are different. This analysis quantifies the therapeutic benefit of SRS by comparative risk analysis. The level of evidence on this topic is low.

Patient reported outcomes and short-term adjustment trajectories following gamma knife radiosurgery for benign brain tumor

PURPOSE

Patient reported outcomes (PROs) in the context of Gamma Knife Stereotactic Radiosurgery (GKSRS) for benign brain tumor have been under-researched. This study examined changes in PROs and adjustment trajectories post-GKSRS.

METHOD

50 adults (54% female) aged on average 53.18 (SD = 14.76) years with benign brain tumor were assessed 1 week before GKSRS, 1-2 weeks post-GKSRS, and at 3-month follow-up. Telephone-based questionnaires of anxiety and depressive symptoms, cognitive function, symptom burden, and health-related quality of life (HRQoL) were completed.

RESULTS

Significant improvements in HRQoL, perceived cognitive ability, anxiety, and total brain tumor symptoms were evident between pre-GKSRS and 3-month follow-up. Conversely, there was a significant short-term increase in depressive symptoms at post-GKSRS; however, levels did not differ from pre-GKSRS at follow-up. No significant changes were evident on PROs of headaches or fatigue. About half of the participants (46-51%) experienced reliable improvement in global HRQoL, and one-third (31-34%) reported improved anxiety symptoms. Increased depressive symptoms was seen in 34% of participants post-GKSRS and 18% at follow-up.

CONCLUSIONS

At 3 months post-GKSRS, improvements in HRQoL, anxiety, perceived cognitive ability, and total brain tumor symptoms were evident. Routine monitoring and support for pre-GKSRS anxiety and depressive symptoms post-GKSRS is recommended.

Repeat Radiosurgery for Sporadic Vestibular Schwannoma After Primary Radiosurgical Failure: An International Multi-institutional Investigation

OBJECTIVE

To describe outcomes of patients with sporadic vestibular schwannoma (VS) who underwent repeat stereotactic radiosurgery (SRS) after primary SRS failure.

STUDY DESIGN

Multi-institutional historical cohort study.

SETTING

Five tertiary care referral centers.

PATIENTS

Adults ≥18 years old with sporadic VS.

INTERVENTION

Primary and repeat treatment with SRS.

MAIN OUTCOME MEASURE

Microsurgery-free survival after repeat SRS.

RESULTS

Across institutions, 32 patients underwent repeat SRS after primary SRS. Most patients (74%) had tumors with cerebellopontine angle extension at primary SRS (median size, 13.5 mm [interquartile range, 7.5-18.8] mm). After primary SRS, patients underwent repeat SRS at a median of 4.8 years (interquartile range, 3.2-5.7 yr). For treatment modality, 30 (94%) patients received gamma knife for primary treatment and 31 (97%) patients received gamma knife as their repeat treatment. Median tumor volume increased from 0.970 cm3 at primary SRS to 2.200 cm3 at repeat SRS. Facial nerve function worsened in two patients after primary SRS and in two patients after repeat SRS. There were no instances of intracranial complications after repeat SRS. Microsurgery-free survival rates (95% confidence interval; number still at risk) at 1, 3, and 5 years after repeat SRS were 97% (90-100%, 24), 84% (71-100%, 13), and 68% (48-96%, 6), respectively. There was one occurrence of malignancy diagnosed after repeat radiosurgery.

CONCLUSION

Overall, repeat SRS for sporadic VS has comparable risk profile, but lower rates of tumor control, compared with primary SRS.

Long-Term Outcome of Unilateral Acoustic Neuromas With or Without Hearing Loss: Over 10 Years and Beyond After Gamma Knife Radiosurgery

BACKGROUND

Since the long-term outcomes of 162 patients who underwent gamma knife radiosurgery (GKS) as an initial or adjuvant treatment for acoustic neuromas (ANs) with unilateral hearing loss were first reported in 1998, there has been no report of a comprehensive analysis of what has changed in GKS practice.

METHODS

We performed a retrospective study of the long-term outcomes of 106 patients with unilateral sporadic ANs who underwent GKS as an initial treatment. The mean patient age was 50 years, and the mean initial tumor volume was 3.68 cm3 (range, 0.10-23.30 cm3). The median marginal tumor dose was 12.5 Gy (range, 8.0-15.0 Gy) and the median follow-up duration was 153 months (range, 120-216 months).

RESULTS

The tumor volume increased in 11 patients (10.4%), remained stationary in 27 (25.5%), and decreased in 68 patients (64.2%). The actuarial 3, 5, 10, and 15-year tumor control rates were 95.3 ± 2.1%, 94.3 ± 2.2%, 87.7 ± 3.2%, and 86.6 ± 3.3%, respectively. The 10-year actuarial tumor control rate was significantly lower in the patients with tumor volumes of ≥ 8 cm3 (P = 0.010). The rate of maintaining the same Gardner-Robertson scale grade was 28.6%, and that of serviceable hearing was 46.4%. The rates of newly developed facial and trigeminal neuropathy were 2.8% and 4.7%, respectively. The patients who received marginal doses of less than 12 Gy revealed higher tumor control failure rates (P = 0.129) and newly occurred facial or trigeminal neuropathy rates (P = 0.040 and 0.313, respectively).

CONCLUSION

GKS as an initial treatment for ANs could be helpful in terms of tumor control, the preservation of serviceable hearing, and the prevention of cranial neuropathy. It is recommended to perform GKS as soon as possible not only for tumor control in unilateral ANs with hearing loss but also for hearing preservation in those without hearing loss.

Long-Term Hearing Outcome After Radiosurgery for Vestibular Schwannoma: A Systematic Review and Meta-Analysis

BACKGROUND

Stereotactic radiosurgery (SRS) is one of the main treatment options in the management of small to medium size vestibular schwannomas (VSs), because of high tumor control rate and low cranial nerves morbidity. Series reporting long-term hearing outcome (>3 years) are scarce.

OBJECTIVE

To perform a systematic review of the literature and meta-analysis, with the aim of focusing on long-term hearing preservation after SRS.

METHODS

Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we reviewed articles published between January 1990 and October 2020 and referenced in PubMed or Embase. Inclusion criteria were peer-reviewed clinical study or case series of VSs treated with SRS (single dose), reporting hearing outcome after SRS with a median or mean audiometric follow-up of at least 5 years. Hearing preservation, cranial nerves outcomes, and tumor control were evaluated.

RESULTS

Twenty-three studies were included. Hearing preservation was found in 59.4% of cases (median follow-up 6.7 years, 1409 patients). Main favorable prognostic factors were young age, good hearing status, early treatment after diagnosis, small tumor volume, low marginal irradiation dose, and maximal dose to the cochlea. Tumor control was achieved in 96.1%. Facial nerve deficit and trigeminal neuropathy were found in 1.3% and 3.2% of patients, respectively, both significantly higher in Linear Accelerator series than Gamma Knife series ( P < .05).

CONCLUSION

Long-term hearing preservation remains one of the main issues after SRS, with a major impact on health-related quality of life. Our meta-analysis suggests that hearing preservation can be achieved in almost 60% of patients after a median follow-up of 6.7 years, irrespective of the technique.

Symptomatic Post-Radiosurgery Intratumoral Hemorrhage in a Case of Vestibular Schwannoma: A Case Report and Review of the Literature

Gamma knife radiosurgery (GKRS) is considered an established treatment for vestibular schwannoma (VS) in selected patients. Spontaneous intratumoral hemorrhage in VS after GKRS is very rare. In this report, we present a 63-year-old gentleman who had right-side severe sensorineural hearing loss on MRI showing a right cerebellopontine angle tumor (volume 4.96 cm3) with an internal acoustic meatus extension. He underwent GKRS with the prescription dose of 12 Gy to the 50% isodose line, covering 4.66 cm3 (i.e., 94%) of the tumor. Ten days later, he experienced a symptomatic intra-lesional hemorrhage with a mass effect over the brainstem. When symptoms did not resolve after an initial conservative approach, he underwent surgical decompression of the lesion. Postoperatively, the patient had facial palsy but was free of disabling vertigo and ataxia. At the 6-month follow-up, he was doing well without any other complaints. Although rare, an intralesional bleed can occur after GKRS in VS and should be suspected when new severe symptoms develop immediately after therapy.

Stereotactic radiotherapy in three weekly fractions for the management of vestibular schwannomas

PURPOSE

This study evaluates the rates of tumor control, hearing preservation and cranial nerve toxicity with the use of CyberKnife stereotactic radiotherapy consisting of 2100 cGy to the 80% isodose line delivered in three weekly fractions to treat vestibular schwannomas.

MATERIALS AND METHODS

Retrospective chart review of vestibular schwannoma patients treated with CyberKnife stereotactic radiotherapy or undergoing watchful waiting between 2006 and 2017 was performed. For inclusion, patients receiving CyberKnife stereotactic radiotherapy must have had pretreatment magnetic resonance imaging and audiography, and 2 follow-up magnetic resonance imaging and audiograms. Watchful waiting patients must have had a minimum of 2 magnetic resonance imaging and 2 audiograms.

RESULTS

Forty patients met inclusion criteria. Twenty-two underwent CyberKnife stereotactic radiotherapy. Eighteen remain in watchful waiting. Crude tumor control was 86.4% at mean radiographic follow-up of 52.3 months. Kaplan-Meier progression-free survival was 76.9% at 5 years. Kaplan-Meier survival from radiographic growth was 61.5% at 5 years. Kaplan-Meier hearing preservation was 17.5% at 5 years. All patients undergoing watchful waiting presenting with serviceable hearing maintained serviceable hearing. Serviceable hearing among CyberKnife stereotactic radiotherapy patients was 42.9% prior to treatment and 14.2% through mean follow-up of 53.7 months. One patient experienced trigeminal nerve toxicity 45 months after SRT. 95.5% of CyberKnife stereotactic radiotherapy patients were complication-free.

CONCLUSIONS

Our fractionation regimen provides tumor control consistent with current literature. Hearing outcomes, however, should be discussed with patients prior to CyberKnife stereotactic radiotherapy.

Postoperative headache following treatment of vestibular schwannoma: A literature review

Vestibular schwannoma (VS) is a brain tumour arising from Schwann cells that is typically closely associated with the vestibulocochlear nerve. Post-operative headaches (POH) are a potentially common complication of surgery for VS. Greatly differing rates of POH have previously been reported, particularly with different surgical approaches. The aim of this review is to identify and summarise the available peer-reviewed evidence on rates of POH following operative (or radiosurgery) treatment for VS, in addition to information about the treatment and prognosis of POH in these patients. A systematic search was conducted of Pubmed, Medline, Scopus and EMBASE in April 2017 using the medical subject headings (acoustic neuroma OR vestibular schwannoma) AND headache. Eligibility determination and data extraction were performed in duplicate with standardised forms. POH is common following surgery for VS. Differing rates of POH have been reported with different management approaches, patient age and tumour size. There are relatively few studies that have directly compared the rates of POH with different surgical approaches. The retrosigmoid approach with craniotomy appears to have lower rates of POH than when the retrosigmoid approach is performed with craniectomy. Patients under the age of 65 and with tumours <1.5 cm in size appear to have a higher risk of POH. The most commonly documented management of POH involves simple analgesia, although the majority of patients report this treatment is of only minimal benefit. Further prospective studies comparing rates of POH following different surgical approaches and radiosurgery are required.

Predictive Factors of Unfavorable Events After Gamma Knife Radiosurgery for Vestibular Schwannoma

OBJECTIVE

Gamma Knife radiosurgery (GKS) for the treatment of vestibular schwannoma (VS) introduces risks to the facial nerve and auditory perception and may involve post-treatment complications such as pseudoprogression, hydrocephalus, and other cranial neuropathies. This study of patients with VS who underwent GKS investigated radiosurgical results, focusing on post-treatment complications and identifying the factors that predict such complications.

METHODS

We undertook a retrospective review of all VS patients treated with the Perfexion Leksell Gamma Knife between November 2007 and October 2010 at our institution. Patients who underwent at least 12 months of clinical and radiologic assessments before and after GKS were included.

RESULTS

All 235 patients were included in the analyses reported here. The 5-year serviceable hearing and facial nerve preservation values were 73.9% and 94.3%, respectively. Following GKS, 43 patients (18.30%) showed pseudoprogression, 15 (6.38%) exhibited hydrocephalus, 22 (9.36%) showed trigeminal neuropathy, 14 (5.96%) showed vertigo, and 25 (10.64%) showed facial myokymia. According to multivariate analysis, solid tumor nature was significantly associated with pseudoprogression and patient age was significantly associated with hydrocephalus. Patients receiving margin doses ≥13 Gy had a significantly higher probability of loss of serviceable hearing. Patients with smaller tumors had a trigeminal nerve preservation rate comparable with patients harboring larger tumors. Patients receiving margin doses <13 Gy or older patients had a significantly higher probability of vestibular nerve dysfunction.

CONCLUSIONS

Further prospective studies should be designed to provide further insight into the exact relationship between the predictive factors we investigated and post-treatment complications.

Gamma Knife radiosurgery for large vestibular schwannomas greater than 3 cm in diameter

OBJECTIVE Stereotactic radiosurgery (SRS) is an important alternative management option for patients with small- and medium-sized vestibular schwannomas (VSs). Its use in the treatment of large tumors, however, is still being debated. The authors reviewed their recent experience to assess the potential role of SRS in larger-sized VSs. METHODS Between 2000 and 2014, 35 patients with large VSs, defined as having both a single dimension > 3 cm and a volume > 10 cm³, underwent Gamma Knife radiosurgery (GKRS). Nine patients (25.7%) had previously undergone resection. The median total volume covered in this group of patients was 14.8 cm³ (range 10.3-24.5 cm³). The median tumor margin dose was 11 Gy (range 10-12 Gy). RESULTS The median follow-up duration was 48 months (range 6-156 months). All 35 patients had regular MRI follow-up examinations. Twenty tumors (57.1%) had a volume reduction of greater than 50%, 5 (14.3%) had a volume reduction of 15%-50%, 5 (14.3%) were stable in size (volume change < 15%), and 5 (14.3%) had larger volumes (all of these lesions were eventually resected). Four patients (11.4%) underwent resection within 9 months to 6 years because of progressive symptoms. One patient (2.9%) had open surgery for new-onset intractable trigeminal neuralgia at 48 months after GKRS. Two patients (5.7%) who developed a symptomatic cyst underwent placement of a cystoperitoneal shunt. Eight (66%) of 12 patients with pre-GKRS trigeminal sensory dysfunction had hypoesthesia relief. One hemifacial spasm completely resolved 3 years after treatment. Seven patients with facial weakness experienced no deterioration after GKRS. Two of 3 patients with serviceable hearing before GKRS deteriorated while 1 patient retained the same level of hearing. Two patients improved from severe hearing loss to pure tone audiometry less than 50 dB. The authors found borderline statistical significance for post-GKRS tumor enlargement for later resection (p = 0.05, HR 9.97, CI 0.99-100.00). A tumor volume ≥ 15 cm³ was a significant factor predictive of GKRS failure (p = 0.005). No difference in outcome was observed based on indication for GKRS (p = 0.0761). CONCLUSIONS Although microsurgical resection remains the primary management choice in patients with VSs, most VSs that are defined as having both a single dimension > 3 cm and a volume > 10 cm³ and tolerable mass effect can be managed satisfactorily with GKRS. Tumor volume ≥ 15 cm³ is a significant factor predicting poor tumor control following GKRS.

Hearing Preservation after Low-dose Gamma Knife Radiosurgery of Vestibular Schwannomas

The objective of the retrospective study was to evaluate the factors associated with hearing preservation after low-dose Gamma Knife radiosurgery (GKS) of vestibular schwannomas performed according to the modern standards. From January 2005 to September 2010, 141 consecutive patients underwent such treatment in Tokyo Women’s Medical University. Mean marginal dose was 11.9 Gy (range, 11–12 Gy). The doses for the brain stem, cranial nerves (V, VII, and VIII), and cochlea were kept below 14 Gy, 12 Gy, and 4 Gy, respectively. Out of the total cohort, 102 cases with at least 24 months follow-up were analyzed. Within the median follow-up of 56 months (range, 24–99 months) the crude tumor growth control was 92% (94 cases), whereas its actuarial rate at 5 years was 93%. Out of 49 patients with serviceable hearing on the side of the tumor before GKS, 28 (57%) demonstrated its preservation at the time of the last follow-up. No one evaluated factor, namely Gardner-Robertson hearing class before irradiation, Koos tumor stage, extension of the intrameatal part of the neoplasm up to fundus, nerve of tumor origin, presence of cystic changes in the neoplasm, and cochlea dose demonstrated statistically significant association with preservation of the serviceable hearing after radiosurgery. In conclusion, GKS of vestibular schwannomas performed according to the modern standards of treatment permits to preserve serviceable hearing on the side of the tumor in more than half of the patients. The actual causes of hearing deterioration after radiosurgery remain unclear.

Safety and Efficacy of Gamma Knife Radiosurgery for the Management of Koos Grade 4 Vestibular Schwannomas

BACKGROUND:

Gamma Knife radiosurgery (GKRS) is commonly used in treating small vestibular schwannomas; however, its use for larger vestibular schwannomas is still controversial.

OBJECTIVE:

To assess the long-term safety and efficacy of treating eligible Koos grade 4 vestibular schwannomas with GKRS.

METHODS:

We conducted a single-center, retrospective evaluation of patient undergoing GKRS for Koos grade 4 vestibular schwannomas. We evaluated clinical, imaging, and treatment characteristics and assessed treatment outcome. Inclusion criteria were tumor size of ≥4 cm3 and follow-up of at least 6 months. Patients with neurofibromatosis type 2 were excluded. Primary outcomes measured were tumor control rate, hearing and facial function preservation rate, and complications. All possible factors were analyzed to assess clinical significance.

RESULTS:

Sixty-eight patients met inclusion criteria. Median follow-up was 47 months (range, 6-125 months). Baseline hearing was serviceable in 60%. Median tumor volume at radiosurgery was 7.4 cm3 (range, 4-19 cm3). The median marginal dose used was 12 Gy at the 50% isodose line. Actuarial tumor control rates were 95% and 92% at 2 and 10 years, respectively. Actuarial serviceable hearing preservation rates were 89% and 49% at 2 and 5 years, respectively. Facial nerve preservation was 100%. Clinical complications included balance disturbance (11%), facial pain (10%), facial numbness (5%), and tinnitus (10%). Most complications were mild and transient. Hydrocephalus occurred in 3 patients, requiring ventriculoperitoneal shunt insertion. Larger tumor size was significantly associated with persisting symptoms post-treatment.

CONCLUSION:

Patients with Koos grade 4 vestibular schwannomas and minimal symptoms can be treated safely and effectively with GKRS.

The Solid Component of Radiographically Non-Growing, Post-Radiated Vestibular Schwannoma Retains Proliferative Capacity: Implications for Patient Counseling

OBJECTIVE

Nearly all radiated vestibular schwannomas (VS) have solid tissue remaining at the radiation bed. The viability and proliferation capacity of this tissue has never been objectively assessed. The goals of our study were to (1) determine whether this tissue retains the morphological and immunohistochemical features of VS and (2) evaluate whether the tissue is capable of proliferation in cell culture.

METHODS

Case history, magnetic resonance imaging (MRI), cell culture, histology, and immunohistochemistry.

RESULTS

We report the first case of a post-radiated, sporadic VS patient whose non-growing, residual MR-enhancing solid tissue was examined histologically and in cell culture. These cells were architecturally identical to non-radiated VS, had a Ki67 proliferative index similar to non-radiated sporadic and NF2-associated VS, were S100 positive, and grew in culture with kinetics comparable to non-radiated VS.

CONCLUSION

The long-term risk for delayed tumor growth and/or secondary malignancy in radiated VS patients is unknown. Because the average life span in the United States is nearly 80 years, patients should be informed that (1) residual VS cells are viable even when tumors appear to be non-growing on MRI, (2) post-radiation surveillance imaging is required indefinitely, and (3) radiation may incur more risk in those patients with life expectancy>20-25 years.