Single Fraction Versus Fractionated Linac-Based Stereotactic Radiotherapy for Vestibular Schwannoma: A Single-Institution Experience

Extra- and intracranial schwannomas treated with fractionated stereotactic irradiation: Results of a retrospective, multicentric study

PURPOSE

Limited data exist on the role of fractionated stereotactic radiotherapy in the therapeutic strategy for neurinomas, particularly for extracranial locations. The objective of this study was to describe intra- and extracranial schwannomas using stereotactic body radiotherapy.

MATERIALS AND METHODS

A multicentric, non-interventional study was conducted using retrospectively collected data between January 2007 and September 2021. Patients who received fractionated stereotactic radiotherapy were included. Patient characteristics, data on localization, acute and chronic toxicity, local control, as well as progressive-free survival were collected.

RESULTS

A total of 72 patients were included with 17 being treated with surgery beforehand. Intracranial localizations concerned nerve VIII (36 lesions), but also nerve IV, V, X and mixed nerves (XII). Extracranial localizations could be cervical, thoracic or lumbar. Treatment regimens were mainly delivering 36Gy in nine fractions of 4Gy (23.6 %) and 21Gy in three fractions of 7Gy (48.6 %). The median follow-up was 49.2 months. Local control was 84.8 % at 3 and 81.8 % at 5 years. Localization and dose schedule did not affect local control (P=0.67 and P=0.46 respectively). Besides surgery, no other factors were associated with local control (P=0.01). Two patients (5.0 %) experienced improvement in their hearing symptoms, while 35 (87.5 %) remained stable.

CONCLUSION

Our large multicentre study results add to evidence that fractionated stereotactic radiotherapy is a safe and effective treatment option for managing intracranial schwannomas but also extracranial localizations, including those of larger sizes.

Treatment options for unilateral vestibular schwannoma: a network meta-analysis

This study aimed to explore the effect of observation, microsurgery, and radiotherapy for patients with vestibular schwannoma (VS). We searched PubMed, Medline, Embase, Web of Science, and Cochrane library from their establishment to July 31, 2024. 34 non-RCTs and 1 RCT that included 6 interventions were analyzed. We found the MS, and different SRS all had better tumor local control rates. Regarding preserved hearing, the order from the highest to the lowest was FSRT 5 fractions, FSRT 3 fractions, SRS, ConFSRT, Observation, and MS. Regarding improvement in the rate of tinnitus, the order from the highest to the lowest was ConFSRT, FSRT 3 fractions, SRS, Observation, MS, and FSRT 5 fractions. In terms of improving the rate of disequilibrium/vertigo, the order from the highest to the lowest was SRS, Observation, FSRT 3 fractions, FSRT 5 fractions, MS, and ConFSRT. In terms of protection of the trigeminal nerve, the order from the highest to lowest was observation, SRS, ConFSRT, FSRT 3 fractions, FSRT 5 fractions, and MS. Lastly, in terms of protection of the facial nerve, the order from the highest to lowest was SRS, ConFSRT, Observation, FSRT 3 fractions, FSRT 5 fractions, and MS. In patients with VS, MS and radiosurgery showed better local tumor control rates; however, compared with MS, different SRS all provided better protection of nerve function and improved the symptoms of vestibular function and tinnitus, among which the best was SRS. Therefore, in these patients, SRS may be a promising alternative treatment.

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.

Single-fraction radiosurgery outcomes for large vestibular schwannomas in the upfront or post-surgical setting: a systematic review and International Stereotactic Radiosurgery Society (ISRS) Practice Guidelines

PURPOSE

To perform a systematic review of literature specific to single-fraction stereotactic radiosurgery (SRS) for large vestibular schwannomas (VS), maximum diameter ≥ 2.5 cm and/or classified as Koos Grade IV, and to present consensus recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

METHODS

The Medline and Embase databases were used to apply the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach. We considered eligible prospective and retrospective studies, written in the English language, reporting treatment outcomes for large VS; SRS for large post-operative tumors were analyzed in aggregate and separately.

RESULTS

19 of the 229 studies initially identified met the final inclusion criteria. Overall crude rate of tumor control was 89% (93.7% with no prior surgery vs 87.7% with prior surgery). Rates of salvage microsurgical resection, need for shunt, and additional SRS in all series versus those with no prior surgery were 9.6% vs 3.3%, 4.7% vs 6.4% and 1% vs 0.9%, respectively. Rates of facial palsy and hearing preservation in all series versus those with no prior surgery were 1.3% vs 3.4% and 34.2% vs 40.4%, respectively.

CONCLUSIONS

Upfront SRS resulted in high rates of tumor control with acceptable rates of facial palsy and hearing preservation as compared to the results in those series including patients with prior surgery (level C evidence). Therefore, although large VS are considered classic indication for microsurgical resection, upfront SRS can be considered in selected patients and we recommend a prescribed marginal dose from 11 to 13 Gy (level C evidence).

Proton beam radiation therapy for vestibular schwannomas-tumor control and hearing preservation rates: a systematic review and meta-analysis

OBJECTIVE

Proton beam therapy is considered, by some authors, as having the advantage of delivering dose distributions more conformal to target compared with stereotactic radiosurgery (SRS). Here, we performed a systematic review and meta-analysis of proton beam for VSs, evaluating tumor control and cranial nerve preservation rates, particularly with regard to facial and hearing preservation.

METHODS

We reviewed, using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) articles published between 1968 and September 30, 2022. We retained 8 studies reporting 587 patients.

RESULTS

Overall rate of tumor control (both stability and decrease in volume) was 95.4% (range 93.5-97.2%, p heterogeneity= 0.77, p<0.001). Overall rate of tumor progression was 4.6% (range 2.8-6.5%, p heterogeneity < 0.77, p<0.001). Overall rate of trigeminal nerve preservation (absence of numbness) was 95.6% (range 93.5-97.7%, I2 = 11.44%, p heterogeneity= 0.34, p<0.001). Overall rate of facial nerve preservation was 93.7% (range 89.6-97.7%, I2 = 76.27%, p heterogeneity<0.001, p<0.001). Overall rate of hearing preservation was 40.6% (range 29.4-51.8%, I2 = 43.36%, p heterogeneity= 0.1, p<0.001).

CONCLUSION

Proton beam therapy for VSs achieves high tumor control rates, as high as 95.4%. Facial rate preservation overall rates are 93%, which is lower compared to the most SRS series. Compared with most currently reported SRS techniques, proton beam radiation therapy for VSs does not offer an advantage for facial and hearing preservation compared to most of the currently reported SRS series.

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.

Dosimetric predictive factors for facial nerve paralysis after cyberknife® stereotactic radiotherapy for vestibular schwannomas: A single institution experience of 88 patients

PURPOSE

To identify dosimetric predictive factors of facial nerve paralysis for patients with vestibular schwannomas (VS) treated in a single institution with Cyberknife® (CK) hypofractionated stereotactic radiotherapy (SRT).

METHODS AND MATERIALS

Eighty-eight patients were treated from 2010 to 2020. Different treatment schedules were used over that period, some prescribed to the 80% isodose line (4 × 5 Gy, 3 × 7 Gy, 3 × 8 Gy and 5 × 5 Gy) and one to the 70% isodose line (3 × 7.7 Gy). Local control tumor and facial nerve toxicity were recorded, as well as various dosimetric indicators.

RESULTS

Median follow-up 37 months (range, 7-96). Of the 88 stereotactic treatments, 20 patients (23%) developed objectively diagnosed radiation-induced facial nerve paralysis. The 2-year and 5-year local tumor control were respectively 95% and 88%, and the overall 2-year facial nerve preservation was 76%. Prescriptions with a maximum dose point (Dmax) of 33 Gy were at a substantially higher risk of facial paralysis than prescriptions with a Dmax less than or equal to 30 Gy (HR = 4.51, 95% CI = [1.04;19.6], p = 0.045). The 2-years cumulative incidences of facial paralysis were 32% [20%;44%] in the case of a 33 Gy Dmax, against 7% [1%;21%] otherwise. We identified four significative dosimetric predictive factors for radiation-induced facial nerve dysfunction: a GTV minimal dose over 22 Gy (EQD2 = 45.5 Gy, p = 0.019), a GTV mean dose over 29 Gy (EQD2 = 73.5 Gy, HR = 2.84, 95% CI = [1.10;7.36], p = 0.024), a PTV mean dose over 27 Gy (EQD2 = 64.8 Gy, HR = 10.52, 95% CI = [1.39;79.76], p = 0.002) and a PTV maximal dose of 32 Gy (EQD2 = 87.5 Gy,HR = 5.09, 95% CI = [1.17;22.15], p = 0.013).

CONCLUSION

We identified four dosimetric predictive factors for post-treatment facial paralysis. Increasing the doses of hypofractionated stereotactic radiotherapy for vestibular schwannomas leads to higher facial nerve toxicity and may lead to lower local control rates than other published series. Our three-hypofractionated regimens may have also played a role in these results.

Vestibular Schwannoma Hypofractionated Stereotactic Radiation Therapy in Five Fractions

AIM

To retrospectively analyse the long-term results of hypofractionated stereotactic radiation therapy (HSRT) applied in five fractions for vestibular schwannomas.

MATERIALS AND METHODS

One hundred and thirty-four patients with vestibular schwannomas underwent medical treatment of HSRT. The median follow-up time interval was 54 months (range 6-121 months). All patients had a prescribed dose of 22 Gy in five fractions to D90. Restaging was carried out by thin-slice contrast-enhanced T1 magnetic resonance imaging. Progression was defined as 2 mm post-treatment tumour enlargement. Progression or death for any reason was counted as an event in progression-free survival rates. Acute toxicity was defined as adverse events occurring within 3 months of HSRT; long-term toxicity was defined as such events occurring after 3 months.

RESULTS

In 74/128 patients who had >6 months of follow-up (54%), the HSRT resulted in a partial or a complete response. The mean time interval for response in 50% of these was 4 years, whereas in 49 patients (38%) vestibular schwannomas failed to show any response, resulting in stable disease. Five of 128 patients (4%) showed marked progressive vestibular schwannomas after treatment in the first 3 years; two of them received conventionally fractionated radiation therapy. Local control at 3, 5 and 7 years was 96%, 95% and 94%, respectively. Seven were lost to follow-up. The median planning target volume was 2.1 ml (range 0.78-8.66). The 3- and 5-year progression-free survival rates were 95% and 94%, respectively. Seven patients reported a marked deterioration in hearing ability. Post-radiation therapy magnetic resonance imaging showed variability in oedema collection, but no patient suffered from radio-necrosis. Grade 2 temporary facial nerve disorders were observed in 10 patients (8%) 3-6 months after HSRT.

CONCLUSION

Delivering HSRT in five fractions for vestibular schwannoma appears safe and efficient, combining both efficiency and short treatment time while optimising neurological function preservation.

Stereotactic radiosurgery ensures an effective and safe long-term control of Koos grade IV vestibular schwannomas: a single-center, retrospective, cohort study

PURPOSE

Stereotactic radiosurgery (SRS) is a standard treatment modality for vestibular schwannomas (VSs). However, there is a paucity of data on tumor control and neurological preservation for larger VSs. We aimed to investigate the long-term effectiveness of SRS for Koos grade IV compared with I-III VSs.

METHODS

We included 452 patients with VSs (50 Koos grade IV and 402 Koos grade I‒III) who were treated with SRS at our institution from 1990 to 2021. Tumor control and functional preservation were calculated using the Kaplan-Meier method and compared between groups with the log-rank test.

RESULTS

The median post-SRS follow-up period was 68 months. Progression-free survival rates were 91% at 5 and 10 years for Koos grade IV VSs, and 95% and 92%, respectively, for Koos grade I‒III VSs (p = 0.278). In Koos grade IV VSs, functional preservation rates of the facial and trigeminal nerves were both 96% at 5 years (both 98% for Koos grade I‒III VSs; facial, p = 0.410; trigeminal, p = 0.107). Hearing preservation rates were 61% at 5 years for Koos grade IV VSs and 78% for Koos grade I-III VSs (p = 0.645). Symptomatic transient tumor expansion was more common with Koos grade IV VSs (8.0% vs. 2.5%, p = 0.034), although all related symptoms diminished in accordance with tumor shrinkage.

CONCLUSION

SRS may contribute to long-term tumor control and adequate neurological preservation in the treatment of Koos grade IV VSs, comparable to those in the treatment of Koos grade I‒III VSs.

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.

Radiotherapy of benign intracranial tumours

We present the updated recommendations of the French Society for Radiation Oncology on benign intracranial tumours. Most of them are meningiomas, vestibular schwannomas, pituitary adenomas, craniopharyngiomas, and glomus tumours. Some grow very slowly, and can be observed without specific treatment, especially if they are asymptomatic. Symptomatic or growing tumours are treated by surgery, which is the reference treatment. When surgery is not possible, due to the location of the lesion, or general conditions, radiotherapy can be applied, as it is if there is a postoperative growing residual tumour, or a local relapse. Indications have to be discussed at a multidisciplinary panel, with precise evaluation of the benefit and risks of the treatments. The techniques to be used are the most modern ones, as multimodal imaging and image-guided radiation therapy. Stereotactic treatments, using fractionated or single doses depending on the size or the location of the tumours, are commonly realized, to avoid as much a possible the occurrence of late side effects.

Tumor Control Following Stereotactic Radiosurgery in Patients with Vestibular Schwannomas - A Retrospective Cohort Study

BACKGROUND

To better counsel vestibular schwannoma patients, it is necessary to understand the tumor control rates of stereotactic radiosurgery (SRS).

OBJECTIVES

To determine tumor control rates, factors determining control and complication rates following SRS.

METHODS

Tertiary hospital retrospective cohort.

RESULTS

579 tumors (576 patients) were treated with SRS. 477 tumors (474 patients, 82%) had ≥1 year follow up and 60% (344) ≥3 years follow up. 88% of tumors had primary SRS and 6.7% salvage SRS. Median follow up time was 4.6 years. At 3 years, the tumor control rate of primary SRS was 89% (258 of 290) in sporadic tumors compared to 43% in Neurofibromatosis type II (3 of 17) (p < 0.01). Our bivariable survival data analysis showed that Neurofibromatosis type II, documented pre-SRS growth, tumor measured by maximum dimension, SRS given as nonprimary treatment increased hazard of failure to control. There was one case of malignancy and another of rapid change following intra-tumoral hemorrhage. For tumors undergoing surgical salvage (25 of 59), 56% had a total or near-total resection, 16% had postoperative CSF leak, with 12% new facial paralysis (House-Brackmann grade VI) and worsening of facial nerve outcomes (House-Brackmann grade worse in 59% at 12 mo).

CONCLUSIONS

Control of vestibular schwannoma after primary SRS occurs in the large majority. Salvage surgical treatment was notable for higher rates of postoperative complications compared to primary surgery reported in the literature.

Long-term clinical outcomes of stereotactic radiosurgery and hypofractionated stereotactic radiotherapy using the CyberKnife® robotic radiosurgery system for vestibular schwannoma

AIM

The study aimed to evaluate the long-term clinical outcomes of patients with vestibular schwannoma (VS) treated with stereotactic radiosurgery (SRS) and hypofractionated stereotactic radiotherapy (HSRT) with frameless robotic whole-body radiosurgery system (CyberKnife^® ).

METHODS

This retrospective analysis of prospectively collected data included 123 consecutive patients with VS treated at the Radiosurgery center, Ramathibodi Hospital, Bangkok, Thailand. SRS was recommended for patients with unserviceable hearing and Koos grade I-III tumors, and HSRT for patients with serviceable hearing or Koos grade III-IV tumors. Between March 2009 and December 2015, 23 patients (19%) were treated with SRS, whereas 100 (81%) received HSRT. The commonly used regimen was 12 Gy in one fraction for SRS and 18 Gy in three fractions for HSRT.

RESULTS

After a median follow-up of 72 months (range: 12-123 months), the 5-year and 8-year progression-free survival (PFS) rates for the whole cohort were 96% and 92%, respectively. The PFS was not significantly different between the SRS and HSRT groups (p = 0.23). Among 28 patients with serviceable hearing in the HSRT group, the 5-year and 8-year hearing preservation rates were 87% and 65%, respectively. The rate of nonauditory complications was 14%. Koos grade III/IV was a predictor of disease progression and was associated with nonauditory complications.

CONCLUSION

SRS and HSRT with the CyberKnife^® system provided excellent long-term tumor control with a low rate of nonauditory complications. HSRT may result in acceptable hearing preservation rates.

Vestibular Schwannoma: Results of Hypofractionated Stereotactic Radiation Therapy

PURPOSE

Our purpose was to study the outcomes of hypofractionated stereotactic radiation therapy (HSRT) in terms of hearing and radiologic response for vestibular schwannomas.

METHODS AND MATERIALS

This was a longitudinal retrospective study at a referral center from 2011 to 2016. All treatments were performed on a Cyberknife device with a dose of 21 Gy (3 × 7 Gy) or 25 Gy (5 × 5 Gy). We assessed tumor response, neurologic outcomes (hearing and facial nerve function), and treatment toxicity.

RESULTS

A total of 82 patients were included. Fifty-three patients were treated with the 3 × 7 Gy scheme and 29 with the 5 × 5 Gy. Sixteen patients (20%) had a previous surgery. The median follow-up was 48 months (range, 12-88 months). We noted 3 recurrences leading to a control rate of 96.3%. In our cohort, predictive factors of vestibular schwannoma growth were a tumor volume >2 mm3 and a conformal index <1.1 (P < .0001). The treatment was well tolerated with only 5 grade III acute toxicities (4 vertigo and 1 headache) and no grade IV or V. As for late toxicity, we noticed 2 cases of mild peripheral facial palsy (House and Brackman grade II) in previously operated patients. There was 46.0% hearing preservation among patients with serviceable hearing after HSRT.

CONCLUSIONS

Our results suggest that HSRT using 3 or 5 fractions is a well-tolerated and effective regimen. These findings are in addition to the few previous hypofractionation studies and contribute to the validity of this treatment modality.

EANO guideline on the diagnosis and treatment of vestibular schwannoma

The level of evidence to provide treatment recommendations for vestibular schwannoma is low compared with other intracranial neoplasms. Therefore, the vestibular schwannoma task force of the European Association of Neuro-Oncology assessed the data available in the literature and composed a set of recommendations for health care professionals. The radiological diagnosis of vestibular schwannoma is made by magnetic resonance imaging. Histological verification of the diagnosis is not always required. Current treatment options include observation, surgical resection, fractionated radiotherapy, and radiosurgery. The choice of treatment depends on clinical presentation, tumor size, and expertise of the treating center. In small tumors, observation has to be weighed against radiosurgery, in large tumors surgical decompression is mandatory, potentially followed by fractionated radiotherapy or radiosurgery. Except for bevacizumab in neurofibromatosis type 2, there is no role for pharmacotherapy.

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.

Stereotactic Radiosurgery for Vestibular Schwannomas: Tumor Control Probability Analyses and Recommended Reporting Standards

PURPOSE

We sought to investigate the tumor control probability (TCP) of vestibular schwannomas after single-fraction stereotactic radiosurgery (SRS) or hypofractionated SRS over 2 to 5 fractions (fSRS).

METHODS AND MATERIALS

Studies (PubMed indexed from 1993-2017) were eligible for data extraction if they contained dosimetric details of SRS/fSRS correlated with local tumor control. The rate of tumor control at 5 years (or at 3 years if 5-year data were not available) were collated. Poisson modeling estimated the TCP per equivalent dose in 2 Gy per fraction (EQD2) and in 1, 3, and 5 fractions.

RESULTS

Data were extracted from 35 publications containing a total of 5162 patients. TCP modeling was limited by the absence of analyzable data of <11 Gy in a single-fraction, variability in definition of "tumor control," and by lack of significant increase in TCP for doses >12 Gy. Using linear-quadratic-based dose conversion, the 3- to 5-year TCP was estimated at 95% at an EQD2 of 25 Gy, corresponding to 1-, 3-, and 5-fraction doses of 13.8 Gy, 19.2 Gy, and 21.5 Gy, respectively. Single-fraction doses of 10 Gy, 11 Gy, 12 Gy, and 13 Gy predicted a TCP of 85.0%, 88.4%, 91.2%, and 93.5%, respectively. For fSRS, 18 Gy in 3 fractions (EQD2 of 23.0 Gy) and 25 Gy in 5 fractions (EQD2 of 30.2 Gy) corresponded to TCP of 93.6% and 97.2%. Overall, the quality of dosimetric reporting was poor; recommended reporting guidelines are presented.

CONCLUSIONS

With current typical SRS doses of 12 Gy in 1 fraction, 18 Gy in 3 fractions, and 25 Gy in 5 fractions, 3- to 5-year TCP exceeds 91%. To improve pooled data analyses to optimize treatment outcomes for patients with vestibular schwannoma, future reports of SRS should include complete dosimetric details with well-defined tumor control and toxicity endpoints.

ESTRO ACROP guideline for target volume delineation of skull base tumors

BACKGROUND AND PURPOSE

For skull base tumors, target definition is the key to safe high-dose treatments because surrounding normal tissues are very sensitive to radiation. In the present work we established a joint ESTRO ACROP guideline for the target volume definition of skull base tumors.

MATERIAL AND METHODS

A comprehensive literature search was conducted in PubMed using various combinations of the following medical subjects headings (MeSH) and free-text words: "radiation therapy" or "stereotactic radiosurgery" or "proton therapy" or "particle beam therapy" and "skull base neoplasms" "pituitary neoplasms", "meningioma", "craniopharyngioma", "chordoma", "chondrosarcoma", "acoustic neuroma/vestibular schwannoma", "organs at risk", "gross tumor volume", "clinical tumor volume", "planning tumor volume", "target volume", "target delineation", "dose constraints". The ACROP committee identified sixteen European experts in close interaction with the ESTRO clinical committee who analyzed and discussed the body of evidence concerning target delineation.

RESULTS

All experts agree that magnetic resonance (MR) images with high three-dimensional spatial accuracy and tissue-contrast definition, both T2-weighted and volumetric T1-weighted sequences, are required to improve target delineation. In detail, several key issues were identified and discussed: i) radiation techniques and immobilization, ii) imaging techniques and target delineation, and iii) technical aspects of radiation treatments including planning techniques and dose-fractionation schedules. Specific target delineation issues with regard to different skull base tumors, including pituitary adenomas, meningiomas, craniopharyngiomas, acoustic neuromas, chordomas and chondrosarcomas are presented.

CONCLUSIONS

This ESTRO ACROP guideline achieved detailed recommendations on target volume definition for skull base tumors, as well as comprehensive advice about imaging modalities and radiation techniques.

Surgical management for large vestibular schwannomas: a systematic review, meta-analysis, and consensus statement on behalf of the EANS skull base section

BACKGROUND AND OBJECTIVE

The optimal management of large vestibular schwannomas continues to be debated. We constituted a task force comprising the members of the EANS skull base committee along with international experts to derive recommendations for the management of this problem from a European perspective.

MATERIAL AND METHODS

A systematic review of MEDLINE database, in compliance with the PRISMA guidelines, was performed. A subgroup analysis screening all surgical series published within the last 20 years (January 2000 to March 2020) was performed. Weighted summary rates for tumor resection, oncological control, and facial nerve preservation were determined using meta-analysis models. This data along with contemporary practice patterns were discussed within the task force to generate consensual recommendations regarding preoperative evaluations, optimal surgical strategy, and follow-up management.

RESULTS

Tumor classification grades should be systematically used in the perioperative management of patients, with large vestibular schwannomas (VS) defined as > 30 mm in the largest extrameatal diameter. Grading scales for pre- and postoperative hearing (AAO-HNS or GR) and facial nerve function (HB) are to be used for reporting functional outcome. There is a lack of consensus to support the superiority of any surgical strategy with respect to extent of resection and use of adjuvant radiosurgery. Intraoperative neuromonitoring needs to be routinely used to preserve neural function. Recommendations for postoperative clinico-radiological evaluations have been elucidated based on the surgical strategy employed.

CONCLUSION

The main goal of management of large vestibular schwannomas should focus on maintaining/improving quality of life (QoL), making every attempt at facial/cochlear nerve functional preservation while ensuring optimal oncological control, thereby allowing to meet patient expectations. Despite the fact that this analysis yielded only a few Class B evidences and mostly expert opinions, it will guide practitioners to manage these patients and form the basis for future clinical trials.

Stereotactic Radiosurgery for Vestibular Schwannomas: Reducing Toxicity With 11 Gy as the Marginal Prescribed Dose

Background

Stereotactic radiosurgery (SRS) is a common treatment option for vestibular schwannomas. Historically, a dose de-escalation of the marginal prescribed dose from 16 Gy to 12–13 Gy has been done to limit toxicity without reducing local control (LC). We aimed to retrospectively report outcomes of Linac-based SRS for vestibular schwannomas treated with different doses.

Methods

Included in the study were 97 stage 1 (1%), 2 (56%), 3 (21.5%), and 4 (21.5%) vestibular schwannomas treated with Linac-based (Novalis^®) SRS from 1995 to 2019. No margin was added to the GTV to create the PTV. The median marginal prescribed dose was 14 Gy (range: 12–16 Gy) before 2006 and then 11 Gy for all patients (61 pts). Mean tumor volume was 1.96 cm³, i.e., about 1.6 cm in diameter. Mean follow-up was 8.2 years.

Results

Following SRS, LC at 3, 5, and 10 years was 100%, 98.4%, and 95.6%, respectively [100% for those with ≤ 13 Gy as the marginal prescribed dose (NS)]. Toxicity to the trigeminal nerve was reported in 7.2% of cases (3.3% and 0% for transient and permanent toxicity for 11 Gy). The marginal prescribed dose was the only significant predictive factor in univariate and multivariate analysis (HR = 1.77, 95% CI = 1.07–3.10, p = 0.028). Toxicity to the facial nerve was reported in 6.2% of cases. The marginal prescribed dose was again the only significant predictive factor in univariate and multivariate analysis (HR = 1.31, 95% CI = 0.77–2.23, p = 0.049).

Conclusion

Linac-based SRS for stages 1–3 vestibular schwannomas provides excellent outcomes: a 10-year LC rate of over 95%, with a permanent facial or trigeminal toxicity rate of under 5%. A marginal prescribed dose of 11 Gy seems to decrease nerve toxicity and facial toxicity in particular, without reducing LC. Prospective studies with longer follow-up are needed.

Health Care Utilization in Patients Undergoing Repeat Stereotactic Radiosurgery for Vestibular Schwannoma with 5-Year Follow-up: A National Database Analysis

Background Stereotactic radiosurgery (SRS) has been used as an alternative to microsurgery in patients with small vestibular schwannoma (VS). We compare health care utilization metrics in patients undergoing repeat-SRS (re-SRS) and no repeat SRS (nr-SRS) at long-term follow-up.

Materials and Methods We queried the MarketScan database using International Classification of Diseases, Ninth Revision and Current Procedural Terminology 4, from 2000 to 2016. We included adult patients who had diagnosis of VS and treatment with SRS with at least 5 years of continuous enrollment after the procedure. Outcomes were hospital admissions, outpatient services, and medication refills.

Results Of 1,047 patients, 5.1% (n = 53) had repeat SRS. Majority of re-SRS (74%, n = 39) were done within 2 years of index procedure and 51% were within 1-year of initial procedure. Patients who required re-SRS incurred higher hospital readmission rate, outpatient services, and had higher payments compared with those who did not require re-SRS at 6 months, 1 year, and 2 years following the initial procedures. Re-SRS received 3.0- and 3.1-times higher payments at 1 and 2 years compared with nr-SRS cohort. At 5 years following SRS, median combined payments for re-SRS cohort was $105286 (interquartile range [IQR] $70999, $156569) compared with $44172 (IQR $22956, $84840) for nr-SRS cohort.

Conclusion More than half of the re-SRS procedures were noted within first year of initial SRS for VS. Overall payments at 5 years for repeat SRS was more than double that for nr-SRS. Repeat SRS was also associated with more re-admissions and outpatient services at annual follow-up time points.

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.

LINAC-based stereotactic radiosurgery versus hypofractionated stereotactic radiotherapy delivered in 3 or 5 fractions for vestibular schwannomas: comparative assessment from a single institution

PURPOSE

The optimal treatment strategy for vestibular schwannoma (VS) is not known, and different radiation techniques and fractionation regimens are currently being used. This report aimed to assess outcomes after LINAC-based radiosurgery (SRS) and hypofractionated radiotherapy (hypo-FSRT) and identify possible differences in outcomes between hypo-FSRT delivered in 3 or 5 fractions.

METHODS

From 2005 to 2017, 136 patients underwent treatment with radiotherapy for VS. Thirty-seven patients received SRS (12 Gy), and 99 received hypo-FSRT. Hypo-FSRT was delivered in 3 fractions (total 18-21 Gy, n = 39) and 5 fractions (total 25 Gy, n = 60).

RESULTS

The median follow-up was 57 months. Eight patients had progression requiring surgery, corresponding to an overall local control rate of 93.4%, with no significant difference between the fractionation schedules. A correlation with borderline significance (p = 0.052) was detected between cystic tumors and local failure. A tendency toward a higher incidence of local failure was observed after 2015 when SRS treatment increased and included slightly larger tumors. Hearing preservation was observed in 35% of patients and 36% of patients experienced acute side effects, but persistent facial or trigeminal nerve toxicity was rare.

CONCLUSION

SRS and hypo-FSRT with 3 or 5 fractions provided a high rate of local control with no significant differences between treatment schedules. SRS is a well-documented radiation technique for VS and is the recommendation for small- to medium-sized tumors. This report demonstrates excellent long-term outcomes after hypo-FSRT; this regimen can be delivered safely and is an alternative for selected patients.

Systematic Review of Hearing Preservation After Radiotherapy for Vestibular Schwannoma

OBJECTIVE

To determine the long-term hearing preservation rate for spontaneous vestibular schwannoma treated by primary radiotherapy.

DATA SOURCES

The MEDLINE/PubMed, Web of Science, Cochrane Reviews, and EMBASE databases were searched using a comprehensive Boolean keyword search developed in conjunction with a scientific librarian. English language papers published from 2000 to 2016 were evaluated.

STUDY SELECTION

Inclusion criteria: full articles, pretreatment and posttreatment audiograms or audiogram based scoring system, vestibular schwannoma only tumor type, reported time to follow-up, published after 1999, use of either Gamma Knife or linear accelerator radiotherapy.

EXCLUSION CRITERIA

case report or series with fewer than five cases, inadequate audiometric data, inadequate time to follow-up, neurofibromatosis type 2 exceeding 10% of study population, previous treatment exceeding 10% of study population, repeat datasets, use of proton beam therapy, and non-English language.

DATA EXTRACTION

Two reviewers independently analyzed papers for inclusion. Class A/B, 1/2 hearing was defined as either pure tone average less than or equal to 50 db with speech discrimination score more than or equal to 50%, American Academy of Otolaryngology-Head & Neck Surgery (AAO-HNS) Hearing Class A or B, or Gardner-Robertson Grade I or II. Aggregate data were used when individual data were not specified.

DATA SYNTHESIS

Means were compared with student t test.

CONCLUSIONS

Forty seven articles containing a total of 2,195 patients with preserved Class A/B, 1/2 hearing were identified for analysis. The aggregate crude hearing preservation rate was 58% at an average reporting time of 46.6 months after radiotherapy treatment. Analysis of time-based reporting shows a clear trend of decreased hearing preservation extending to 10-year follow-up. This data encourages a future long-term controlled trial.

Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines on Hearing Preservation Outcomes in Patients With Sporadic Vestibular Schwannomas

Question 1

What is the overall probability of maintaining serviceable hearing following stereotactic radiosurgery utilizing modern dose planning, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled that there is moderately high probability (>50%-75%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 2

Among patients with AAO-HNS (American Academy of Otolaryngology-Head and Neck Surgery hearing classification) class A or GR (Gardner-Robertson hearing classification) grade I hearing at baseline, what is the overall probability of maintaining serviceable hearing following stereotactic radiosurgery, utilizing modern dose planning, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled that there is a high probability (>75%-100%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 3

What patient- and tumor-related factors influence progression to nonserviceable hearing following stereotactic radiosurgery using ≤13 Gy to the tumor margin?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled regarding the probability of successful hearing preservation based on the following prognostic data: the most consistent prognostic features associated with maintenance of serviceable hearing are good preoperative word recognition and/or pure tone thresholds with variable cut-points reported, smaller tumor size, marginal tumor dose ≤12 Gy, and cochlear dose ≤4 Gy. Age and sex are not strong predictors of hearing preservation outcome.

Question 4

What is the overall probability of maintaining serviceable hearing following microsurgical resection of small to medium-sized sporadic vestibular schwannomas early after surgery, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering microsurgical resection should be counseled that there is a moderately low probability (>25%-50%) of hearing preservation immediately following surgery, moderately low probability (>25%-50%) of hearing preservation at 2 yr, moderately low probability (>25%-50%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 5

Among patients with AAO-HNS class A or GR grade I hearing at baseline, what is the overall probability of maintaining serviceable hearing following microsurgical resection of small to medium-sized sporadic vestibular schwannomas early after surgery, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering microsurgical resection should be counseled that there is a moderately high probability (>50%-75%) of hearing preservation immediately following surgery, moderately high probability (>50%-75%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 6

What patient- and tumor-related factors influence progression to nonserviceable hearing following microsurgical resection of small to medium-sized sporadic vestibular schwannomas?

Recommendation

Level 3: Individuals who meet these criteria and are considering microsurgical resection should be counseled regarding the probability of successful hearing preservation based on the following prognostic data: the most consistent prognostic features associated with maintenance of serviceable hearing are good preoperative word recognition and/or pure tone thresholds with variable cut-points reported, smaller tumor size commonly less than 1 cm, and presence of a distal internal auditory canal cerebrospinal fluid fundal cap. Age and sex are not strong predictors of hearing preservation outcome.

Question 7

What is the overall probability of maintaining serviceable hearing with conservative observation of vestibular schwannomas at 2, 5, and 10 yr following diagnosis?

Recommendation

Level 3: Individuals who meet these criteria and are considering observation should be counseled that there is a high probability (>75%-100%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 8

Among patients with AAO-HNS class A or GR grade I hearing at baseline, what is the overall probability of maintaining serviceable hearing with conservative observation at 2 and 5 yr following diagnosis?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled that there is a high probability (>75%-100%) of hearing preservation at 2 yr, and moderately high probability (>50%-75%) of hearing preservation at 5 yr. Insufficient data were available to determine the probability of hearing preservation at 10 yr for this population subset.

Question 9

What patient and tumor-related factors influence progression to nonserviceable hearing during conservative observation?

Recommendation

Level 3: Individuals who meet these criteria and are considering observation should be counseled regarding probability of successful hearing preservation based on the following prognostic data: the most consistent prognostic features associated with maintenance of serviceable hearing are good preoperative word recognition and/or pure tone thresholds with variable cut-points reported, as well as nongrowth of the tumor. Tumor size at the time of diagnosis, age, and sex do not predict future development of nonserviceable hearing during observation.  The full guideline can be found at: https://www.cns.org/guidelines/guidelines-manage-ment-patients-vestibular-schwannoma/chapter_3.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

Facial Nerve Paralysis Occurring 4 Days following Stereotactic Radiosurgery for a Vestibular Schwannoma

Stereotactic radiosurgery (SRS) is commonly used for the treatment of vestibular schwannomas given its high rate of tumor control and low rate of complications. Facial nerve palsy has been reported several months after treatment as a rare late complication of SRS. Here, we report a case of facial weakness occurring only 4 days after treatment and discuss potential etiology and management considerations.

Progression of hearing loss after LINAC-based stereotactic radiotherapy for vestibular schwannoma is associated with cochlear dose, not with pre-treatment hearing level

Background

Although stereotactic radiotherapy (SRT) for vestibular schwannoma has demonstrated excellent local control rates, hearing deterioration is often reported after treatment. We therefore wished to assess the change in hearing loss after SRT and to determine which patient, tumor and treatment-related factors influence deterioration.

Methods

We retrospectively analyzed progression of hearing loss in patients with vestibular schwannoma who had received stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) as a primary treatment between 2000 and 2014. SRS had been delivered as a single fraction of 12 Gy, and patients treated with FSRT had received 30 fractions of 1.8 Gy. To compare the effects of SRS and FSRT, we converted cochlear doses into EQD₂. Primary outcomes were loss of functional hearing, Gardner Robertson (GR) classes I and II, and loss of baseline hearing class. These events were used in Kaplan Meier plots and Cox regression. We also calculated the rate of change in Pure Tone Average (PTA) in dB per month elapsed after radiation—a measure we use in linear regression—to assess the associations between the rate of change in PTA and age, pre-treatment hearing level, tumor size, dose scheme, cochlear dose, and time elapsed after treatment (time-to-first-audiogram).

Results

The median follow-up was 36 months for 67 SRS patients and 63 months for 27 FSRT patients. Multivariate Cox regression and in linear regression both showed that the cochlear V90 was significantly associated with the progression of hearing loss. But although pre-treatment PTA correlated with rate of change in Cox regression, it did not correlate in linear regression. The time-to-first-audiogram was also significantly associated, indicating time dependency of the rate of change. None of the analysis showed a significant difference between dose schemes.

Conclusions

We found no significant difference between SRS and FSRT. As the deterioration in hearing after radiotherapy for vestibular schwannoma was associated with the cochlea V90, restricting the V90 may reduce progression of hearing loss. The association between loss of functional hearing and baseline PTA seems to be biased by the use of a categorized variable for hearing loss.

Fractionated Proton Beam Therapy for Acoustic Neuromas: Tumor Control and Hearing Preservation

Purpose

This prospective cohort evaluated patients with acoustic neuroma treated with proton irradiation at Loma Linda University Medical Center. A dose of 50.4 Gy in 28 fractions was given to improve hearing preservation while maintaining tumor control.

Patients and Methods

Ninety-five patients were treated from March 1991 to March 2008. Fractionated proton radiotherapy at daily doses of 1.8 Gy was employed. Patients were treated to 1 of 3 total doses: 59.4 Gy, used initially for patients without serviceable hearing; 54 Gy, used for patients with serviceable hearing through October 2000; and 50.4 Gy used since 2001 for patients with serviceable hearing. Survival and local control were calculated using the Kaplan-Meier method. Logistic regression analysis was preformed comparing dose, tumor size, and tumor location with hearing preservation.

Results

Ninety-four patients were assessable; the median follow-up was 64 months. Five-year local control rates for the 59.4 Gy, 54 Gy, and 50.4 Gy groups were 95%, 97%, and 92%, respectively (P = .80); the overall 10-year actuarial control rate was 90%. Cranial nerve injuries occurred in <5% in all groups. Four-year actuarial rates of hearing preservation were maintained in 44% of patients treated with 54 Gy and 64% treated with 50.4 Gy (P = .284). On multivariate analysis, initial tumor diameter (≤1.5 cm) was found to be a prognostic factor for maintaining serviceable hearing in both groups (P = .011).

Conclusions

Fractionated proton therapy of 50.4 Gy offers excellent local control and minimal cranial nerve toxicities. Improved rates of hearing preservation that are comparable with radiosurgery were seen with 50.4 Gy compared with higher doses, although this did not reach significance. Maintaining hearing was found to be associated with smaller initial tumor size.

Upfront Gamma Knife surgery for facial nerve schwannomas: retrospective case series analysis and systematic review

INTRODUCTION

Facial nerve schwannomas are rare tumors and account for less than 2% of intracranial neurinomas, despite being the most common tumors of the facial nerve. The optimal management is currently under debate and includes observation, microsurgical resection, radiosurgery (RS), and fractionated radiotherapy. Radiosurgery might be a valuable alternative, as a minimally invasive technique, in symptomatic patients and/or presenting tumor growth.

METHODS

We review our series of four consecutive cases, treated with Gamma Knife surgery (GKS) between July 2010 and July 2017 in Lausanne University Hospital, Switzerland. Clinical and dosimetric parameters were assessed. Radiosurgery was performed using Leksell Gamma Knife Perfexion. We additionally performed a systematic review, which included 23 articles and 193 treated patients from the current literrature.

RESULTS

The mean age at the time of the GKS was 44.25 years (median 43.5, range 34-56). Mean follow-up period was 31.8 months (median 36, range 3-60). Two cases presented with facial palsy and other two with hemifacial spasm. Pretherapeutically, House-Brackmann (HB) grade was II for one case, III for two, and VI for one. The mean gross tumor volume (GTV) was 0.406 ml (median 0.470 ml, range 0.030-0.638 ml). The mean marginal prescribed dose was 12 Gy at the mean 54% isodose line (median 50%, range 50-70). The mean prescription isodose volume (PIV) was 0.510 ml (median 0.596 ml, range 0.052-0.805 ml). The mean dose received by the cochlea was 4.2 Gy (median 4.1 Gy, range 0.1-10). One patient benefited from a staged-volume GKS. At last follow-up, tumor volume was stable in one and decreased in three cases. Facial palsy remained stable in two patients (one HB II and one HB III) and improved in two (from HB III to II and from HB VI to HB III). Regarding hemifacial spasm, both patients presenting one pretherapeutically had a decrease in its frequency and intensity after GKS. All patients kept stable Gardner-Robertson class 1 at last follow-up.

CONCLUSION

In our experience, RS and particularly GKS, using standard, yet low doses of radiation, appear to be a safe and effective therapeutic option in the management of these rare tumors. The results as from our systematic review are also encouraging with satisfactory rates of clinical stabilization and/or improvement and high rate of tumor control. Complications are infrequent and mostly transient.

Long-term hearing outcomes after gamma knife surgery in patients with vestibular schwannoma with hearing preservation: evaluation in 92 patients with serial audiograms

The treatment strategy for patients with vestibular schwannoma (VS) is controversial, and data concerning the long-term hearing outcomes > 5 years after gamma knife surgery (GKS) are limited. The long-term hearing outcomes after GKS were evaluated in VS patients with hearing preservation. Ninety-two VS patients with a pure tone average (PTA) ≤ 50 dB were evaluated. The median age was 54 years; the median tumor volume was 1.5 cm³. The tumors were treated with a median margin dose of 12 Gy and a median mean cochlear dose of 4.0 Gy. At the time of GKS, 65 patients retained a PTA of 0-30 dB, and 27 had a PTA of 31-50 dB. The median follow-up period was 106 months. At the final follow-up, 2 (2%) developed tumor progression. During the median audiogram follow-up of 83 months, the PTA was ≤ 30 dB in 22 patients (24%) and 31-50 dB in 27 patients (29%); 43 patients (47%) worsened to a PTA > 50 dB. Hearing preservation rates were 66, 57, and 44% at 3, 5, and 10 years, respectively. In multivariate analysis, the mean cochlear dose (P < 0.001) and pre-GKS PTA (P = 0.045) were significant for hearing preservation. GKS was an effective treatment option for VS patients with a PTA ≤ 50 dB. As a lower cochlear dose and better pre-GKS PTA contributed to long-term hearing preservation, prophylactic GKS before hearing deterioration or tumor growth would be a treatment of choice if patients provided informed consent.

Management of Vestibular Schwannomas with Linear Accelerator-Based Stereotactic Radiosurgery: A Single Center Experience

Aims and background

The primary goal of treatment for vestibular schwannoma is to achieve local control without comprimising regional cranial nerve function. Stereotactic radiosurgery has emerged as a viable therapeutic option for vestibular schwannoma. The aim of the study is to report our 15-year single center experience using linear accelerator-based stereotactic radiosurgery in the management of patients with vestibular schwannoma.

Methods and study design

Between July 1998 and January 2013, 68 patients with unilateral vestibular schwannoma were treated using stereotactic radiosurgery at the Department of Radiation Oncology, Gulhane Military Medical Academy. All patients underwent high-precision stereotactic radiosurgery using a linear accelerator with 6-MV photons.

Results

Median follow-up time was 51 months (range, 9–107). Median age was 45 years (range, 20–77). Median dose was 12 Gy (range, 10–13) prescribed to the 85%-95% isodose line encompassing the target volume. Local tumor control in patients with periodic follow-up imaging was 96.1%. Overall hearing preservation rate was 76.5%.

Conclusions

Linear accelerator-based stereotactic radiosurgery offers a safe and effective treatment for patients with vestibular schwannoma by providing high local control rates along with improved quality of life through well-preserved hearing function.

Peripheral nervous system injury after high-dose single-fraction image-guided stereotactic radiosurgery for spine tumors

OBJECTIVE The object of this study was to determine the percentage of high-dose (1800-2600 cGy) single-fraction stereotactic radiosurgery (SF-SRS) treatments to the spine that result in peripheral nervous system (PNS) injury. METHODS All patients treated with SF-SRS for primary or metastatic spine tumors between January 2004 and May 2013 and referred to the Rehabilitation Medicine Service for evaluation and treatment of neuromuscular, musculoskeletal, or functional impairments or pain were retrospectively identified. RESULTS Five hundred fifty-seven SF-SRS treatments in 447 patients resulted in 14 PNS injuries in 13 patients. All injures resulted from SF-SRS delivered to the cervical or lumbosacral spine at 2400 cGy. The overall percentage of SF-SRS treatments resulting in PNS injury was 2.5%, increasing to 4.5% when the thoracic spine was excluded from analysis. The median time to symptom onset following SF-SRS was 10 months (range 4-32 months). The plexus (cervical, brachial, and/or lumbosacral) was affected clinically and/or electrophysiologically in 12 (86%) of 14 cases, the nerve root in 2 (14%) of 14, and both in 6 (43%) of 14 cases. All patients experienced pain and most (93%) developed weakness. Peripheral nervous system injuries were CTCAE Grade 1 in 14% of cases, 2 in 64%, and 3 in 21%. No dose relationship between SF-SRS dose and PNS injury was detected. CONCLUSIONS Single-fraction SRS to the spine can result in PNS injury with major implications for function and quality of life.

Radiotherapeutic management of vestibular schwannomas using size- and location-adapted fractionation regimens to maximize the therapeutic ratio

BACKGROUND

We evaluated and compared the radiographic and clinical outcomes of patients with vestibular schwannomas treated with single fraction stereotactic radiosurgery (SRS), 5 fractions of hypofractionated stereotactic radiation therapy (hSRT), or 25 to 30 fractions of conventionally fractionated stereotactic radiation therapy (cfSRT).

METHODS AND MATERIALS

Fifty-six patients treated with LINAC-based SRS (median, 12.5 Gy), hSRT (25 Gy), or cfSRT (median, 54 Gy) were retrospectively reviewed. Fractionation was based on the size of the tumor, proximity to the brainstem, and potential risk of neurological sequelae. Median follow-up time was 55.2 months.

RESULTS

The pretreatment median tumor diameter was significantly smaller for SRS (1.14 cm) compared with hSRT (1.7 cm) (P = .03) and cfSRT (2.0 cm) (P < .001). The overall local tumor control was 96.4%: 100% SRS, 100% hSRT, and 90% cfSRT (P = .19). Tumor regression was observed in 53.3% of SRS, 76.2% of hSRT, and 90% of cfSRT (P = .05). There was less transient expansion of tumors treated with cfSRT (5%) than with SRS (53.3%) or hSRT (28.6%) (P = .005). The median time to regression was 13.8 months for SRS, 14.2 months for hSRT, and 5.5 months for cfSRT (P = .34). There was a 3.6% incidence of grade 3 trigeminal neuropathy, but there was no grade 3 facial neuropathy.

CONCLUSIONS

All 3 regimens demonstrated similar excellent local control with minimal toxicity; however, the ability of hSRT to treat larger tumors with comparable outcomes to SRS and greater patient convenience when compared with cfSRT suggest that hSRT may offer the optimal treatment approach.

Vestibular Schwannomas Treated with Cyberknife®: Clinical Outcomes

Purpose

Fractionated stereotactic radiotherapy (FSR) is a recognized treatment for vestibular schwannomas (VS). This study's aim is to present clinical outcomes and local control (LC) results for patients with VS treated with FSR using the Cyberknife® (CK) in 2 French cancer centers.

Methods

Patients treated with FSR for VS between 2007 and 2012 were retrospectively analyzed. Local control was determined using follow-up MRI. The hearing preservation (HP) rate was determined by analyzing pretreatment and posttreatment audiograms.

Results

Forty patients were treated for VS with the CK in both centers. The mean maximal VS dimension was 18.3 mm (range 3–30). The median follow-up was 36 months and the LC was 97% at 3 years of follow-up and 89% after 5 years. The HP rate was 83% and no facial nerve impairment was reported.

Conclusions

Our results in terms of LC and HP rate are congruent with similar studies that use the CK to treat VS. It appears that the CK is safe and efficient in VS management even for large lesions. Further studies with larger cohorts are warranted.

[Computer-controlled high-precision radiation]

The irradiation of tumors in the brain is challenging due to the proximity of radiation sensitive critical structures and the tumors to be treated. In addition, irradiation above a certain level can cause irreversible damage to nerve tissue. The irradiation of benign and malignant brain tumors requires precise techniques to preserve critical structures while simultaneously administering a high radiation dose for maximum effectiveness. Therefore, stereotaxy, as a subspecialty of neurosurgery, has developed various irradiation techniques, e. g., intracerebral application of interstitial brachytherapy (SBT; stereotactic brachytherapy) and stereotactic radiosurgery (SRS). Due to the development of computer-controlled radiation techniques (e. g., Cyberknife) over the last 20 years, SRS has gained increasing importance.

Radiotherapy for vestibular schwannoma: Review of recent literature results

BACKGROUND

The management of vestibular schwannoma is still a quite controversial issue and can include wait and see policy, surgery and radiotherapy, mainly with stereotactic technique. The purpose of this study is to review the results of recent clinical series treated by radiotherapy.

MATERIALS AND METHODS

Literature search was performed by Pubmed and Scopus by using the words "vestibular schwannoma, acoustic neuroma, radiotherapy, radiosurgery".

RESULTS

Management options of VS include wait and see, surgery and radiotherapy. In case of small lesions, literature data report local control rates higher than 90% after radiosurgery (SRS) similar those of surgical techniques. Recent literature reviews show favourable functional outcome by using SRS. Several literature data support the use of fractionated stereotactic radiotherapy (FSRT) in case of large inoperable lesions.

CONCLUSION

Radiotherapy plays a relevant role in the treatment of VS. In small-size lesions, SRS can guarantee similar local control and potentially better function outcome compared to surgery. In case of large and irregularly shaped lesions, FSRT can be the used when surgery is not feasible.

Gamma Knife surgery for patients with jugular foramen schwannomas: a multiinstitutional retrospective study in Japan

OBJECTIVE This study aimed to explore the efficacy and safety of stereotactic radiosurgery in patients with jugular foramen schwannomas (JFSs). METHODS This study was a multiinstitutional retrospective analysis of 117 patients with JFSs who were treated with Gamma Knife surgery (GKS) at 18 medical centers of the Japan Leksell Gamma Knife Society. The median age of the patients was 53 years. Fifty-six patients underwent GKS as their initial treatment, while 61 patients had previously undergone resection. At the time of GKS, 46 patients (39%) had hoarseness, 45 (38%) had hearing disturbances, and 43 (36%) had swallowing disturbances. Eighty-five tumors (73%) were solid, and 32 (27%) had cystic components. The median tumor volume was 4.9 cm³, and the median prescription dose administered to the tumor margin was 12 Gy. Five patients were treated with fractionated GKS and maximum and marginal doses of 42 and 21 Gy, respectively, using a 3-fraction schedule. RESULTS The median follow-up period was 52 months. The last follow-up images showed partial remission in 62 patients (53%), stable tumors in 42 patients (36%), and tumor progression in 13 patients (11%). The actuarial 3- and 5-year progression-free survival (PFS) rates were 91% and 89%, respectively. The multivariate analysis showed that pre-GKS brainstem edema and dumbbell-shaped tumors significantly affected PFS. During the follow-up period, 20 patients (17%) developed some degree of symptomatic deterioration. This condition was transient in 12 (10%) of these patients and persistent in 8 patients (7%). The cause of the persistent deterioration was tumor progression in 4 patients (3%) and adverse radiation effects in 4 patients (3%), including 2 patients with hearing deterioration, 1 patient with swallowing disturbance, and 1 patient with hearing deterioration and hypoglossal nerve palsy. However, the preexisting hoarseness and swallowing disturbances improved in 66% and 63% of the patients, respectively. CONCLUSIONS GKS resulted in good tumor control in patients with either primary or residual JFSs. Although some patients experienced some degree of symptomatic deterioration after treatment, persistent adverse radiation effects were seen in only 3% of the entire series at the last follow-up. Lower cranial nerve deficits were extremely rare adverse radiation effects, and preexisting hoarseness and swallowing disturbances improved in two-thirds of patients. These results indicated that GKS was a safe and reasonable alternative to surgical resection in selected patients with JFSs.

Vestibular Schwannoma: The Evolution of Hearing and Tumor Size in Natural Course and after Treatment by LINAC Stereotactic Radiosurgery

OBJECTIVE

To review the natural course of tumor size and hearing during conservative management of 151 patients with unilateral vestibular schwannoma (VS), and to evaluate the same parameters for the part of the group (n = 84) who were treated by LINAC stereotactic radiosurgery (SRS).

METHODS

In prospectively collected data, patients underwent MRI and complete audiovestibular tests at inclusion, during the conservative management period and after SRS. Hearing was graded according to the Gardner-Robertson (GR) scale and tumor size according to Koos. Statistics were performed using Kaplan-Meier survival analysis and multivariate analyses including linear and logistic regression. Specific insight was given to patients with serviceable hearing.

RESULTS

During the conservative management period (mean follow-up time: 24 months, range: 6-96), the annual risk of GR class degradation was 6% for GRI and 15% for GR II patients. Hearing loss as an initial symptom was highly predictive of further hearing loss (p = 0.003). Tumor growth reached 25%. For SRS patients, functional hearing preservation was 51% at 1 year and 36% at 3 years. Tumor control was 94 and 91%, respectively.

CONCLUSION

In VS patients, hearing loss at the time of diagnosis is a predictor of poorer hearing outcome. LINAC SRS is efficient for tumor control. Patients who preserved their pretreatment hearing presented less hearing loss per year after SRS than before treatment, suggesting a protective effect of SRS when cochlear function can be preserved.

Stereotactic Radiosurgery versus Natural History in Patients with Growing Vestibular Schwannomas

Objective To describe our experience with stereotactic radiosurgery and its efficacy on growing tumors, and then to compare this result with the natural history of a similar cohort of non-radiation-treated lesions. Study Design A retrospective chart review and cohort comparison. Methods The long-term control rates of patients having undergone radiosurgery were collected and calculated, and this population was then compared with a group of untreated patients from the same period of time with growing lesions. Results A total of 61 patients with growing vestibular schwannomas treated with radiosurgery were included. After a mean of 160 months, we observed a control rate of 85.2%. When compared with a group of 36 patients with growing tumors who were yet to receive treatment (previously published), we found a corrected control rate or relative risk reduction of only 76.8%. Conclusion Radiosurgery for growing vestibular schwannomas is less effective than previously reported in unselected series. Although radiosurgery still has a role in managing this disease, consideration should be given to the actual efficacy that may be calculated when the natural history is known. We hope other centers will similarly report their experience on this cohort of patients.

Nonsteroidal anti-inflammatory medications are cytostatic against human vestibular schwannomas

Vestibular schwannomas (VSs) are the most common tumors of the cerebellopontine angle. Significant clinical need exists for pharmacotherapies against VSs. Motivated by previous findings that immunohistochemical expression of cyclooxygenase 2 (COX-2) correlates with VS growth rate, we investigated the role of COX-2 in VSs and tested COX-2 inhibiting salicylates against VSs. COX-2 was found to be aberrantly expressed in human VS and primary human VS cells in comparison with control human nerve specimens and primary Schwann cells (SCs), respectively. Furthermore, levels of prostaglandin E2, the downstream enzymatic product of COX-2, were correlated with primary VS culture proliferation rate. Because COX-2 inhibiting salicylates such as aspirin are well tolerated and frequently clinically used, we assessed their repurposing for VS. Changes in proliferation, cell death, and cell viability were analyzed in primary VS cultures treated with aspirin, sodium salicylate, or 5-aminosalicylic acid. These drugs neither increased VS cell death nor affected healthy SCs. The cytostatic effect of aspirin in vitro was in concurrence with our previous clinical finding that patients with VS taking aspirin demonstrate reduced tumor growth. Overall, this work suggests that COX-2 is a key modulator in VS cell proliferation and survival and highlights salicylates as promising pharmacotherapies against VS.

The biology of radiosurgery and its clinical applications for brain tumors

Stereotactic radiosurgery (SRS) was developed decades ago but only began to impact brain tumor care when it was coupled with high-resolution brain imaging techniques such as computed tomography and magnetic resonance imaging. The technique has played a key role in the management of virtually all forms of brain tumor. We reviewed the radiobiological principles of SRS on tissue and how they pertain to different brain tumor disorders. We reviewed the clinical outcomes on the most common indications. This review found that outcomes are well documented for safety and efficacy and show increasing long-term outcomes for benign tumors. Brain metastases SRS is common, and its clinical utility remains in evolution. The role of SRS in brain tumor care is established. Together with surgical resection, conventional radiotherapy, and medical therapies, patients have an expanding list of options for their care. Clinicians should be familiar with radiosurgical principles and expected outcomes that may pertain to different brain tumor scenarios.