Gamma Knife Radiosurgery for Vestibular Schwannoma

"Salvage surgery for vestibular schwannomas after failed stereotactic radiosurgery or radiation: A systematic review and meta-analysis"

INTRODUCTION

Stereotactic radiosurgery effectively controls vestibular schwannoma (VS). However, in certain cases, microsurgical resection may be necessary for tumor progression after radiosurgery or, after failure of the latter. The results on the safety and efficacy of salvage surgery for VS are still unclear, with scarce literature on the subject.

OBJECTIVE

The present study aimed to evaluate the safety and efficacy of salvage surgery on the resection of vestibular schwannomas that have been previously treated with stereotactic radiosurgery or radiotherapy.

METHODS

Following PRISMA guidelines, we searched Medline, Embase, and Web of Science databases. We used single proportion analysis with 95 % confidence intervals under a random-effects model, I2 to assess heterogeneity, and Baujat and sensitivity analysis to address high heterogeneity. Eligible studies included those with ≥ 4 patients treated with salvage surgery to resection of vestibular schwannomas after failure of stereotactic radiosurgery or radiotherapy.

RESULTS

Of the 1841 initially identified studies, 18 were selected, involving 455 patients, with a median follow-up of 33 months. The combined analysis showed a 69 % (CI: 58 % - 79 %) rate of good clinical outcomes. Regarding partial resection, the pooled analysis confirmed a 48 % rate (CI: 33 % to 63 %) and a 52 % complete resection rate (CI: 37 % to 67 %). The pooled analysis confirmed a 95 % hearing preservation rate in patients undergoing the retrosigmoid approach (CI: 90 % to 100 %) and a 78 % facial nerve preservation rate (CI: 72 % to 84 %). Regarding complications, the pooled analysis confirmed a 20 % complication rate (CI: 14 % to 28 %). There were no deaths related to the procedure.

CONCLUSION

Based on the results, our meta-analysis identified that rescue surgery has been shown to be safe and effective for resection of vestibular schwannomas after failure of stereotactic radiosurgery or radiotherapy, based on good facial nerve preservation rate and total lesion resection rate.

Dynamic contrast-enhanced magnetic resonance imaging for evaluating early response to radiosurgery in patients with vestibular schwannoma

PURPOSE

This study aimed to use dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to evaluate early treatment response in vestibular schwannoma (VS) patients after radiosurgery.

METHODS

Twenty-four VS patients who underwent gamma knife radiosurgery were prospectively followed up for at least four years. DCE-MRI sequences, in addition to standard MRI protocol, were obtained prior to radiosurgery, at 3 and 6 months. Conventionally, treatment responses based on tumor volume changes were classified as regression or stable (RS), transient tumor enlargement (TTE), and continuous tumor enlargement (CTE). DCE-MRI parameters, such as K^trans, K_ep and V_e, were compared according to follow-up periods and between groups. The diagnostic performance was tested using receiver operating characteristic (ROC) curves.

RESULTS

Changes in tumor volume were as follows at the last 48 months of follow-up: RS in 11 patients (45.8%), TTE in 10 patients (41.7%), and CTE in three patients (12.5%). The median time required to distinguish TTE from CTE using conventional MRI was 12 months (range 9-18). The K^trans and V_e were significantly decreased in patients with RS and TTE at 3 and 6 months, but did not differ significantly in patients with CTE. There were no significant differences in K^trans and V_e between patients with RS and TTE at 3 and 6 months. Both K^trans and V_e demonstrated high diagnostic performance in evaluating early treatment response to radiosurgery in patients with VS.

CONCLUSION

DCE-MRI may aid in the monitoring and early prediction of treatment response in patients with VS following radiosurgery.

Primary treatment of small-to-medium (<3cm) sporadic vestibular schwannomas: A systematic review and meta-analysis on hearing preservation and tumor control rates for microsurgery versus radiosurgery

BACKGROUND

A meta-analysis of sporadic VS patients primarily treated with stereotactic radiosurgery (SRS) or microsurgery (MS) was performed, and hearing preservation outcome (HPO), tumor control (TC), and facial nerve dysfunction (FND) were analyzed.

METHODS

A systematic review was conducted (Medline and Scopus database) for the period, January 2010 to June 2020 with appropriate MeSH. English language articles for small-to-medium sporadic VS (<3cm) utilizing SRS or MS as primary treatment modality, with minimum follow-up of 3 years, were included. Studies had to report an acceptable standardized hearing metric.

RESULTS

Thirty-two studies met inclusion criteria: 10 (microsurgery); 23 (radiosurgery); (one comparative study included in both). HPO, at ∼65 months follow-up, were comparable between MS group (10 studies; 809 patients) and SRS group (23 studies; 1234 patients) (56% versus 59%, p=0.1527). TC, at ∼70 months follow-up, was significantly better in MS group (9 studies; 1635 patients) versus SRS group (19 studies; 2260 patients) (98% versus 92%, p < 0.0001). FND, at ∼ 12 months follow-up, was significantly higher in MS group (8 studies; 1101 patients) versus SRS group (17 studies; 2285 patients) (10% versus 2%, p < 0.0001).

CONCLUSION

MS and SRS are comparable primary treatments for small (<3cm) sporadic VS with respect to HPO at 5-year follow-up in patients with serviceable hearing at presentation; ∼50% patients for both modalities will likely lose serviceable hearing by that time-point. High TC rates (>90%) were seen with both modalities; MS (98%) versus SRS (92%). The post-treatment FND was significantly less with SRS group (2%) versus MS group (10%).

Non surgical treatment of vestibular schwannoma

INTRODUCTION AND OBJECTIVES

To evaluate the results of local control and complications in the treatment of vestibular schwannoma treated with radiation.

METHODS

A retrospective study of 194 patients diagnosed with vestibular schwannoma, treated consecutively with radiation (either stereotactic radiosurgery or fractionated radiotherapy) from 1997 to 2012. We analyze the local control of tumors, as well as secondary complications to treatment with radiation.

RESULTS

A total of 132 (68%) tumors 68% are grade I-II tumors of the Koos classification, 40 (19%) are grade III, and 22 (13%) are grade IV. The tumors associated with neurofibromatosis (NF2), are 3.6% (6 tumors in 4 patients). The tumor control for the overall serie is 97% at 5 years, with a median follow-up of 80.4 months. For large tumors the local control is 91% at 5 years. Free survival of chronic complications is 89% at 5 years. Additionally, 50 tumors were subjected to regular follow-up with MRI without treatment, and 28 (58%) did not experienced tumor growth.

CONCLUSIONS

Radiation and follow up with MRI, are an alternative to surgery in the treatment of vestibular schwannoma, with a low level of complications inside of multidisciplinary approach.

Microsurgery versus stereotactic radiation for small vestibular schwannomas: a meta-analysis of patients with more than 5 years' follow-up

OBJECTIVE

To compare the long-term outcome of hearing and tumor outcome of small vestibular schwannomas treated with stereotactic radiation and microsurgery.

DATA SOURCES

A thorough search for English-language publications and "in process" articles dating from 1948 to December 2011 was conducted using Ovid MEDLINE.

STUDY SELECTION

The principal criteria were patients having had microsurgery or radiation therapy as their sole treatment, with a follow-up of at least 5 years, and a useful hearing level at diagnosis.

DATA EXTRACTION

Sixteen studies met our criteria. Hearing preservation outcome (worse or preserved) and tumor outcome (failure, control) data, as well as all other significant observations, were collected from the articles. Stereotactic radiation was the only radiation therapy analyzed.

DATA SYNTHESIS

The Pearson χ test was our primary statistical analysis.

CONCLUSION

Stereotactic radiation showed significantly better long-term hearing preservation outcome rates than microsurgery (p < 0.001). However, long-term tumor outcome was not significantly different in stereotactic radiation as compared with microsurgery (p = 0.122). Although stereotactic radiation demonstrates a more favorable long-term hearing preservation outcome as compared with microsurgery, additional studies are required to provide the medical field with a better understanding of vestibular schwannoma treatment.

Neurofibromatosis

The "neurofibromatoses" are a set of distinct genetic disorders that have in common the occurrence of tumors of the nerve sheath. They include NF1, NF2, and schwannomatosis. All are dominantly inherited with a high rate of new mutation and variable expression. NF1 includes effects on multiple systems of the body. The major NF1-associated tumor is the neurofibroma. In addition, clinical manifestations include bone dysplasia, learning disabilities, and an increased risk of malignancy. NF2 includes schwannomas of multiple cranial and spinal nerves, especially the vestibular nerve, as well as other tumors such as meningiomas and ependymomas. The schwannomatosis phenotype is limited to multiple schwannomas, and usually presents with pain. The genes that underlie each of the disorders are known: NF1 for neurofibromatosis type 1, NF2 for neurofibromatosis type 2, and INI1/SMARCB1 for schwannomatosis. Genetic testing is possible to identify mutations. Insights into pathogenesis are beginning to suggest new treatment strategies, and therapeutic trials with several new forms of treatment are underway.

Surgical treatment of patients with vestibular schwannomas after failed previous radiosurgery

OBJECT

An increasing number of patients with vestibular schwannomas (VSs) are being treated with radiosurgery. Treatment failure or secondary regrowth after radiosurgery, however, has been observed in 2%-9% of patients. In large tumors that compress the brainstem and in patients who experience rapid neurological deterioration, surgical removal is the only reasonable management option.

METHODS

The authors evaluated the relevance of previous radiosurgery for the outcome of surgery in a series of 28 patients with VS. The cohort was further subdivided into Group A (radiosurgery prior to surgery) and Group B (partial tumor removal followed by radiosurgery prior to current surgery). The functional and general outcomes in these 2 groups were compared with those in a control group (no previous treatment, matched characteristics). RESULTS There were 15 patients in Group A, 13 in Group B, and 30 in the control group. The indications for surgery were sustained tumor enlargement and progression of neurological symptoms in 12 patients, sustained tumor enlargement in 15 patients, and worsening of neurological symptoms without evidence of tumor growth in 1 patient. Total tumor removal was achieved in all patients in Groups A and B and in 96.7% of those in the control group. There were no deaths in any group. Although no significant differences in the neurological morbidity or complication rates after surgery were noted, the risk of new cranial nerve deficits and CSF leakage was highest in patients in Group B. Patients who underwent previous radiosurgical treatment (Groups A and B) tended to be at higher risk of developing postoperative hematomas in the tumor bed or cerebellum. The rate of facial nerve anatomical preservation was highest in those patients who were not treated previously (93.3%) and decreased to 86.7% in the patients in Group A and to 61.5% in those in Group B. Facial nerve function at follow-up was found to correlate to the previous treatment; excellent or good function was seen in 87% of the patients from the control group, 78% of those in Group A, and 68% of those in Group B.

CONCLUSIONS

Complete microsurgical removal of VSs after failed radiosurgery is possible with an acceptable morbidity rate. The functional outcome, however, tends to be worse than in nontreated patients. Surgery after previous partial tumor removal and radiosurgery is most challenging and related to worse outcome.

Stereotactic radiation treatment of vestibular schwannoma: indications, limitations, and outcomes

PURPOSE OF REVIEW

Stereotactic radiation treatment is an increasingly performed procedure for patients with vestibular schwannoma and other benign skull base tumors. During the past 30 years, advancements in stereotactic imaging, radiation delivery techniques, and dose planning have improved overall patient outcomes. The specific role of radiation in current management strategies for vestibular schwannoma continues to evolve as long-term outcome data are analyzed and standardized studies are performed. The recent literature regarding the indications, limitations, and outcomes for stereotactic radiation treatment is reviewed.

RECENT FINDINGS

Systematic reviews of the Gamma Knife literature demonstrate improved overall outcomes with radiation doses below 13 Gy. Observation of small vestibular schwannomas is recommended over early radiation or microsurgical intervention. Radiation may be used as adjunctive therapy for large tumors and in certain postradiation treatment failures. Stereotactic radiosurgery and fractionated radiotherapy are equally effective treatment modalities.

SUMMARY

Long-term outcome data will ultimately define future indications and limitations for the use of stereotactic radiation with benign skull base lesions. Current evidence supports its use for small to medium sized primary and recurrent vestibular schwannomas with optimal dosing below 13 Gy. It is also recommended for adjunctive therapy, recurrent tumors, in poor surgical candidates, and for those who do not desire observation or surgery.