Hearing Preservation for Vestibular Schwannomas Treated with Stereotactic Radiosurgery or Fractionated Stereotactic Radiotherapy

Comparison of Stereotactic Radiosurgery and Hypofractionated Radiosurgery for Vestibular Schwannomas: A Meta-Analysis of Available Literature

BACKGROUND

Stereotactic radiosurgery (SRS) and recently, hypofractionated radiosurgery (hSRS) are increasingly utilized as treatment for vestibular schwannomas (VS). We performed a meta-analysis of literature comparing these modalities.

METHODS

The PubMed database of articles was searched for studies that compared SRS and hSRS in patients with VS. Variables analyzed include tumor control, hearing preservation, facial nerve preservation, trigeminal nerve preservation, and total complications. Heterogeneity across the studies was gauged using Higgins's inconsistency index. Funnel plots and Egger's regression intercept test were used to address the publication bias.

RESULTS

Thirteen studies that satisfied the search criteria were selected for meta-analysis. The studies identified in our study included 353 SRS and 511 hSRS-treated patients. Analysis of heterogeneity showed that hSRS is employed for relatively larger tumor sizes in comparison to SRS. Pooled meta-analysis estimates showed no significant differences between SRS and hSRS in terms of tumor control (odds ratio [OR], 0.620; 95% confidence interval [CI], 0.21-1.86, P = 0.39), hearing preservation (OR, 1.07; 95% CI, 0.59-1.93, P = 0.83), facial nerve preservation (OR, 0.53; 5% CI, 0.23-1.21, P = 0.13), or trigeminal nerve preservation (OR, 0.67; 95% CI, 0.24-1.89, P = 0.49) at a mean follow-up of 39 months. Statistically significant heterogeneity was found across the studies only for tumor diameter (Higgins's inconsistency index = 65.69%, P = 0.003) but not for other variables.

CONCLUSIONS

Meta-analysis of thirteen studies comparing SRS and hSRS as treatment for VS showed comparable tumor control, hearing preservation, facial nerve preservation, and trigeminal nerve preservation.

The Effectiveness of Diffusion Tensor Imaging in Determining Radiological Response after Radiosurgery in Patients with Vestibular Schwannoma

BACKGROUND

The effectiveness of Diffusion Tensor Imaging (DTI) in demonstrating functional changes in the tumor in determining the response to treatment after radiosurgery in patients with vestibular schwannoma (VS) is not clear yet.

OBJECTIVE

The study aimed to determine the change in total tumor volume (TTV) in terms of radiological response in patients who had VS and were treated with radiosurgery and investigated the relationship between the TTV, follow-up times and DTI parameters.

METHODS

Thirty-one patients were assessed using DTI and MRI. TTV, apparent diffusion coefficient (ADC), and fractional anisotropy (FA) were calculated. Patients were divided into three groups: those who responded to the treatment (group 1) (n=11), those who did not (group 0) (n=9) and those who remained stable (group 2) (n=11).

RESULTS

The mean duration of follow-up was 28.81±14 months. ADC values increased in patients with VS after radiosurgery (p=0.004). There was no statistical difference in the FA values. A significant reduction in TTV after radiosurgery was detected in group 1 (p=0.003). ADC values increased significantly after radiosurgery in group 2 (p=0.04). Although there were no significant differences, ADC values after radiosurgery increased in group 1 and group 0.

CONCLUSIONS

ADC values continuously increase due to radiation damage in the period before the tumor volume shrinks after radiosurgery. We think that it is not appropriate to diagnose inadequate treatment or progression only when TTV is evaluated in terms of response to treatment in the early period after radiosurgery.

Evaluation of Brainstem Subcortical Auditory Pathways with Diffusion Tensor Imaging After Gamma Knife Radiosurgery in Intracanalicular Vestibular Schwannoma

Objective

To investigate changes in DTI (Diffusion Tensor Imaging) parameters in brainstem subcortical auditory pathways after Gamma Knife Radiosurgery (GKR) in patients with intracanalicular vestibular schwannoma (ICVS) and to analyze the relationship between tumor volume and ADC (apparent diffusion coefficient) and FA (fractional anisotropy) values.

Method

Seventeen patients with ICVS were evaluated before and after GKR. ADC and FA values of the lateral lemniscus (LL) and inferior colliculus (IC) and tumor volume were calculated. Patients who responded to GKR were classified as Group 1 and those who did not respond adequately as Group 2. The relationship between ADC and FA values and changes in tumor volume were analyzed.

Results

Tumor volume significantly decreased after GKR. ADC values obtained from the tumor increased after GKR (p:0.002). There was no significant difference in LL and IC before and after GKR in terms of FA and ADC values (n:17). There was a positive correlation between response to treatment and contralateral LL ADC values after GKR (p=0.005, r:0.652). There was a negative correlation between contralateral IC FA values after GKR and response to treatment (p=0.017, r: -0.568). There was a significant difference between Groups 1 and 2 in regards to contralateral LL ADC (p=0.03) and IC FA values (p=0.017).

Conclusion

Since the cochlear nerve and subcortical auditory pathways have low regeneration potential after nerve damage, ADC and FA changes in LL and IC may be explained with the presence of intracanalicular tumors prior to GKR. Since GKR does not cause additional damage to the subcortical auditory pathways at the brainstem level, we think that GKR is a noninvasive treatment method that can be used safely in patients with ICVS.

Outcomes of stereotactic radiosurgery for large vestibular schwannomas: a systematic review and meta-analysis

Background

Large vestibular schwannomas (VS) pose a treatment challenge for both microsurgery (MS) and stereotactic radiosurgery (SRS). Technical developments have allowed for safer irradiation of large tumors. It remains unclear if SRS can achieve appropriate tumor control and acceptable cranial nerve toxicities. In this study, we assess outcomes of irradiation for large VS.

Methods

PubMed MEDLINE, EMBASE, Web of Science, and Cochrane were searched for all the studies assessing SRS outcome in large VS. Primary endpoints included clinical and radiographic tumor control, need for salvage surgery, serviceable hearing, cranial nerve V and VII impairment, presence of hydrocephalus requiring shunting, and presence of vertigo/dizziness.

Results

Twenty-two studies were identified that met selection criteria for analysis from an initial pool of 1272 reports. They were evaluated according to treatment protocol: 1) single-dose SRS (13 studies, 483 patients), 2) combination of MS and SRS (7 studies, 182 patients), and 3) fractionated SRS (3 studies, 82 patients). Tumor control was achieved in 89%, 94%, and 91% of patients, respectively. Odds ratios (ORs) of post- over pretreatment serviceable hearing were 0.42 (P < .01), 0.47 (P = .05), and 0.60 (P = .22); for facial nerve impairment, these ORs were 1.08 (P = .69), 3.45 (P = .28), and 0.87 (P = .71), respectively.

Conclusions

The management of large VS remains challenging. All treatment modalities resulted in high tumor control rates and worsening of pretreatment hearing. None, however, caused significant facial nerve impairment, suggesting that management strategies incorporating focal irradiation can be successful.

Efficacy and comorbidities of hypofractionated and single-dose radiosurgery for vestibular schwannomas: a systematic review and meta-analysis

Background

Vestibular schwannomas (VS) are tumors of the cerebellopontine angle with significant morbidity, causing hearing loss, tinnitus, and trigeminal and facial nerve compromise. An effective alternative to microsurgical resection is stereotactic radiosurgery (SRS), which can be delivered in either single-fraction (SRS) or hypofractionated stereotactic radiotherapy (hSRT) (3-5 treatments) regimens. It remains unclear which fractionation regimen provides superior outcomes.

Methods

Ovid MEDLINE, EMBASE, CINAHL, and Cochrane Reviews were searched for studies either comparing hSRT with SRS or focusing on hSRT alone in treating VS. Primary endpoints included tumor control, serviceable hearing, tinnitus, and cranial nerve V and VII symptoms. A random-effects analysis was employed to compare pre- and post-treatment effects (hSRT alone) or SRS and hSRT outcomes (two-arm studies).

Results

This analysis included 21 studies focusing on hSRT alone and 13 studies comparing SRS and hSRT. Significant heterogeneity was observed. Overall, when hSRT was analyzed alone, crude tumor control was achieved in 94% (95% CI: 88%, 99%) of 1571 patients. There was no difference between pre- and post-treatment odds ratios (OR) of tinnitus, facial, or trigeminal impairment. Serviceable hearing was diminished following hSRT (OR = 0.60, 95% CI: 0.44, 0.83). Comparison with SRS showed no difference with respect to tumor control, serviceable hearing, trigeminal or facial nerve impairment.

Conclusions

hSRT achieved excellent tumor control and, with the exception of serviceable hearing, did not result in worse post-treatment cranial nerve symptomatology. Analysis of comparative studies between hSRT and SRS did not reveal any significant difference in either tumor control or treatment morbidities.

Impact of Treatment on Vestibular Schwannoma-Associated Symptoms: A Prospective Study Comparing Treatment Modalities

OBJECTIVE

The degree to which various treatment modalities modify vestibular schwannoma (VS)-associated symptoms has received limited attention. The purpose of this study was to determine how different treatment modalities affect subjective symptoms in those presenting with VS.

STUDY DESIGN

Prospective survey.

SETTING

Tertiary neurotology referral center.

METHODS

Patients with sporadic VS who received treatment at our institution were prospectively surveyed with a VS symptom questionnaire. Those who completed a baseline survey prior to treatment and at least 1 posttreatment survey were included. The prospective survey evaluated the severity of self-reported symptoms (Likert scale, 1-10), including tinnitus, dizziness or imbalance, headaches, and hearing loss.

RESULTS

A total of 244 patients were included (mean age, 57 years). The mean duration of follow-up was 2.1 years, and the median number of surveys completed was 2 (interquartile range, 1-3). Seventy-eight (32%) cases were managed with observation, 118 (48%) with microsurgery, and 48 (20%) with radiosurgery. Multivariable analyses revealed no statistically significant difference in the change in tinnitus (P = .15), dizziness or imbalance (P = 0.66), or headaches (P = .24) among treatment groups. Evaluation of clinically important differences demonstrated that microsurgery leads to significant bidirectional changes in headaches.

CONCLUSIONS

Limited prospective data exist regarding the progression or resolution of subjective symptoms in those presenting with VS. This study suggests that tinnitus, dizziness or imbalance, and headaches are unlikely to be significantly modified by treatment modality and generally should not be used to direct treatment choice.

Progressive Vestibular Schwannoma following Subtotal or Near-Total Resection: Dose-Escalated versus Standard-Dose Salvage Stereotactic Radiosurgery

Objective  Local failure of incompletely resected vestibular schwannoma (VS) following salvage stereotactic radiosurgery (SRS) using standard doses of 12 to 13 Gy is common. We hypothesized that dose-escalated SRS, corrected for biologically effective dose, would have superior local control of high-grade VS progressing after subtotal or near-total resection compared with standard-dose SRS. Design  Retrospective cohort study. Setting  Tertiary academic referral center. Participants  Adult patients treated with linear accelerator-based SRS for progressive VS following subtotal or near-total resection. Main Outcome Measures  Dose-escalated SRS was defined by a biologically effective dose exceeding a single-fraction 13-Gy regimen. Study outcomes were local control and neurologic sequelae of SRS. Binary logistic regression was used to evaluate predictors of study outcomes. Results  A total of 18 patients with progressive disease following subtotal (71%) and near-total (39%) resection of Koos grade IV disease (94%) were enrolled. Of the 18 patients, 7 were treated with dose-escalated SRS and 11 with standard-dose SRS. Over a median follow-up of 32 months after SRS, local control was 100% in the dose-escalated cohort and 91% in the standard-dose cohort ( p  = 0.95). Neurologic sequelae occurred in 28% of patients, including 60% of dose-escalated cohort and 40% of the standard-dose cohort ( p  = 0.12), although permanent neurologic sequelae were low at 6%. Conclusions  Dose-escalated SRS has similar local control of recurrent VS following progression after subtotal or near-total resection and does not appear to have higher neurologic sequalae. Larger studies are needed.