Early changes in volume and non-enhanced volume of acoustic neurinoma after stereotactic gamma-radiosurgery

Treatment for vestibular schwannoma: Systematic review and single arm meta-analysis

OBJECTIVE

Vestibular schwannoma is a benign tumor in the schwannoma cells of the 8th cranial nerve. It causes symptoms like tinnitus, vertigo and end up with loss of hearing so the appropriate treatment is very important. There are many treatment techniques including conservative, surgery and radiosurgery. We aimed to systematically review and single arm meta-analysis the different treatment techniques of vestibular schwannoma.

METHODS

A comprehensive literature search using thirteen databases including PubMed, Scopus, and Web of Science was performed. All clinical trials about treatment vestibular schwannoma were included and single arm meta-analyzed. We assessed the risk of bias using ROBIN-I's tool and scale of Council Australia's Cancer Guidelines Wiki. The protocol was registered in PROSPERO (CRD42018089784) and has been updated on 17 April 2019.

RESULTS

A total of 35 clinical trials studies were included in the final analysis. The pooled proportion of stable hearing capability in patients receiving gamma knife radiosurgery (GKRS) was 64% (95% CI: 52%-74%). GKRS favored increased hearing capability 10% (95% CI: 7%-16%). Regarding tumor size, GKRS is the most protective method 53% (95% CI: 37%-69%). Complications occurred most commonly in single fractional linac stereotactic radiosurgery (SFSRT) 37% (95% CI: 12%-72%).

CONCLUSION

Our analysis suggested gamma knife radiosurgery could be the most ideal treatment for vestibular schwannoma based on stabilizing hearing capability, increasing hearing capability, decreasing tumor size and complications.

Non-audiofacial morbidity after Gamma Knife surgery for vestibular schwannoma

OBJECT

While many studies have been published outlining morbidity following radiosurgical treatment of vestibular schwannomas, significant interpractitioner and institutional variability still exists. For this reason, the authors conducted a systematic review of the literature for non-audiofacial-related morbidity after the treatment of vestibular schwannoma with radiosurgery.

METHODS

The authors performed a comprehensive search of the English-language literature to identify studies that published outcome data of patients undergoing radiosurgery treatment for vestibular schwannomas. In total, 254 articles were found that described more than 50,000 patients and were analyzed for satisfying the authors' inclusion criteria. Patients from these studies were then separated into 2 cohorts based on the marginal dose of radiation: < or = 13 Gy and > 13 Gy. All tumors included in this study were < 25 mm in their largest diameter.

RESULTS

A total of 63 articles met the criteria of the established search protocol, which combined for a total of 5631 patients. Patients receiving > 13 Gy were significantly more likely to develop trigeminal nerve neuropathy than those receiving < 13 Gy (p < 0.001). While we found no relationship between radiation dose and the rate of developing hydrocephalus (0.6% for both cohorts), patients with hydrocephalus who received doses > 13 Gy appeared to have a higher rate of symptomatic hydrocephalus requiring shunt treatment (96% [> 13 Gy] vs 56% [< or = 13 Gy], p < 0.001). The rates of vertigo or balance disturbance (1.1% [> 13 Gy] vs 1.8% [< or = 13 Gy], p = 0.001) and tinnitus (0.1% [> 13 Gy] vs 0.7% [< or = 13 Gy], p = 0.001) were significantly higher in the lower dose cohort than those in the higher dose cohort.

CONCLUSIONS

The results of our review of the literature provide a systematic summary of the published rates of nonaudiofacial morbidity following radiosurgery for vestibular schwannoma.

Significant temporal evolution of diffusion anisotropy for evaluating early response to radiosurgery in patients with vestibular schwannoma: findings from functional diffusion maps

BACKGROUND AND PURPOSE

Outcome evaluation in clinical oncology is conventionally based on long-term volumetric changes in the tumor size. The purpose of this study was to prospectively investigate the usefulness of fDMs in incorporating anisotropic diffusion in the evaluation of early response after radiosurgery in patients with vestibular schwannoma.

MATERIALS AND METHODS

The MD, FA, and IVDC were calculated by using simple averaging methods and fDMs. Six patients with vestibular schwannoma treated with stereotactic radiosurgery underwent longitudinal DTI studies on a 3T MR imaging scanner (maximum follow-up, 6 months). Posttreatment DTI data were spatially coregistered with pretreatment scans.

RESULTS

Tumors did not change significantly in size until 6 months after treatment. Diffusion indices changed significantly during the study period. There was a transient decrease in averaged MD followed by a significant increase. IVDC showed an opposite behavior compared with MD. FA decreased continuously throughout the study period. Functional diffusion maps showed a heterogeneous response of tumors to treatment, thereby providing complementary information to simple averaged values.

CONCLUSIONS

DTI allows early detection of therapeutic-induced changes in patients with vestibular schwannoma. Functional diffusion maps incorporating anisotropic diffusion may aid in assessing the heterogeneity of the therapeutic response in this patient group.

Diagnostic accuracy of the constructive interference in steady state sequence alone for follow-up imaging of vestibular schwannomas

BACKGROUND AND PURPOSE

Vestibular schwannoma (VS) is a benign, slow-growing tumor, and radiologic monitoring is an acceptable alternative to surgery in small lesions and in elderly patients. MR imaging with contrast is the study of choice in the follow-up of these lesions. However, gadolinium-based contrast agents have side effects and should be used only when definitely indicated. The purpose of this study was to evaluate the diagnostic accuracy of the constructive interference in steady state (CISS) sequence used without postcontrast sequences for the follow-up imaging of VS.

MATERIALS AND METHODS

MR imaging examinations of 18 patients were retrospectively evaluated by 2 radiologists. VS masses were measured on both CISS and the postcontrast images by each observer. For each patient, the masses were also assessed qualitatively for possible progression between every consecutive study.

RESULTS

Fifty MR images of 18 patients were evaluated. Patients had 1-5 follow-up studies. The mean time interval between the consecutive studies was 23 months (6-55 months). The sensitivity, specificity, and accuracy of the CISS sequence for the detection of progression were 100%. There was good interobserver and intraobserver (CISS and postcontrast) correlation. The CISS sequence had, however, limited sensitivity for the detection of changes in the internal architecture.

CONCLUSIONS

Noncontrast CISS-only technique may be a viable alternative to routine contrast-enhanced sequences for the follow-up of overall lesion size in patients with VS; however, treatment-related changes internal to the tumor are less noticeable using the CISS sequence.

Linear accelerator radiosurgery for vestibular schwannoma: measuring tumor volume changes on serial three-dimensional spoiled gradient-echo magnetic resonance images

OBJECT

The authors report on a series of 46 patients harboring vestibular schwannomas (VSs) treated using linear accelerator (LINAC) radiosurgery and an analysis of serial magnetic resonance (MR) imaging data, specifically the changes in tumor volume.

METHODS

Fifty-three consecutive patients underwent LINAC radiosurgery for VS between 1993 and 2002. Seven of these patients were lost to follow up. Three-dimensional (3D) spoiled gradient-echo (SPGR) MR imaging was performed at 3- to 4-month intervals after radiosurgery. Tumor volume was measured on Gd-enhanced MR images of each slice. The median duration of follow-up MR imaging studies was 56.5 months (range 12-120 months). Follow-up imaging studies were conducted for longer than 1 year in 42 of 53 patients. Tumor volume changes were categorized into four types: enlargement (eight lesions [19%]), no change (two lesions [4.8%]), transient enlargement followed by shrinkage (19 lesions [45.2%]), and direct shrinkage (13 lesions [31%]). Two cases (4.8%) with twice the initial tumor volume required repeated radiosurgery. All cases of transient enlargement had subsequent shrinkage within 2 years after radiosurgery. Nine (21.4%) of 42 patients demonstrated ventricular enlargement on MR images obtained after radiosurgery. Three patients (7.1%) required placement of a ventriculoperitoneal shunt because of symptomatic hydrocephalus, and another four cases (9.5%) spontaneously resolved.

CONCLUSIONS

Volume measurement on 3D-SPGR MR imaging was a suitable method to assess tumor changes. Volume changes beyond twofold or continuous enlargement for longer than 2 years after radiosurgery are key criteria in rating the effects of radiation. Some cases of hydrocephalus after radiosurgery resolved spontaneously and their rates of occurrence were similar to the typical incidence of hydrocephalus associated with VS.