Hearing preservation after low dose linac radiosurgery for acoustic neuroma depends on initial hearing and time

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.

Prediction of hearing preservation after acoustic neuroma surgery based on SMOTE-XGBoost

Prior to the surgical removal of an acoustic neuroma, the majority of patients anticipate that their hearing will be preserved to the greatest possible extent following surgery. This paper proposes a postoperative hearing preservation prediction model for the characteristics of class-imbalanced hospital real data based on the extreme gradient boost tree (XGBoost). In order to eliminate sample imbalance, the synthetic minority oversampling technique (SMOTE) is applied to increase the number of underclass samples in the data. Multiple machine learning models are also used for the accurate prediction of surgical hearing preservation in acoustic neuroma patients. In comparison to research results from existing literature, the experimental results found the model proposed in this paper to be superior. In summary, the method this paper proposes can make a significant contribution to the development of personalized preoperative diagnosis and treatment plans for patients, leading to effective judgment for the hearing retention of patients with acoustic neuroma following surgery, a simplified long medical treatment process and saved medical resources.

Predictors of long-term tumor control after stereotactic radiosurgery for Koos grade 4 vestibular schwannomas

PURPOSE

To evaluate the predictors of long-term tumor control following stereotactic radiosurgery (SRS) for Koos grade 4 vestibular schwannomas (VSs).

METHODS

Overall, 203 sporadic VS patients with compression of the brainstem were treated with SRS. The median tumor volume was 6.7 cm³ (range, 2.0-28.9 cm³) and the median marginal dose was 12 Gy (range, 9-13.5 Gy).

RESULTS

The median follow-up period was 152 months (range, 12-277 months). Tumor control (TC) rates at 3, 5, and 10 years were 89%, 85%, and 82%, respectively. Operation-free survival (OFS) rates at 3, 5, and 10 years were 92%, 85%, and 83%, respectively. Middle cerebellar peduncle (MCP) compression on pre-SRS magnetic resonance imaging scans was significant for both TC (p < 0.001, hazard ratio 1.332) and OFS (p < 0.001, hazard ratio 1.306). The 3-, 5-, and 10-year OFS rates were 98%, 94%, and 92% in the low-risk group (MCP compression < 9.8 mm and > 48 years old), and 58%, 25%, and 17% in high-risk group (MCP compression ≥ 9.8 mm and ≤ 48 years old), respectively. Ten patients (4.9%) developed delayed cyst-related complications. Eleven patients (5.4%) developed newly developed or worsened trigeminal neuralgia. No patient developed persistent facial palsy as an adverse radiation effect. A ventricular peritoneal shunt was required in six patients (3%) who developed hydrocephalus after SRS.

CONCLUSION

SRS is an acceptable treatment option in selected patients with Koos grade 4 VSs. Risk group classification based on patient age and MCP compression is useful in decision-making of Koos grade 4 VSs.

Epidemiology of vestibular schwannoma in the United States, 2004-2016

Background

Vestibular schwannomas (VS) are nonmalignant tumors of the eighth cranial nerve and are the most common nonmalignant nerve sheath tumor. This study provides the most comprehensive and current analysis of VS epidemiology in the United States.

Methods

Incidence data were obtained from the Central Brain Tumor Registry of the United States, from 2004 to 2016 for VS. Age-adjusted incidence rates (AAIRs), rate ratios (AAIRRs), and prevalence ratios (AAPRs) per 100 000 were analyzed by age, sex, race and ethnicity, and laterality. Additional analyses were performed to assess differences in treatment, laterality, and diagnostic confirmation.

Results

Incidence of VS was highest among adults (aged 65–74 years, AAIR: 3.18, 95% confidence interval [CI]: 3.15–3.25). However, there was a much higher distribution of bilateral tumors compared to unilateral in children aged 0–19 years (28.5% vs 1.0%, P < .001). VS incidence was highest among white non-Hispanics (AAIR:1.30, 95% CI: 1.29–1. 31) and lowest among black non-Hispanics. Incidence of radiographically confirmed VS increased from 2004 to 2016 (annual percent change: 1.64, 95% CI: 0.15–3.16, P = .03). For treatment, 40.1% received surgery, while only 23.7% received radiation. There were an estimated 44 762 prevalent cases of VS in 2016 (AAPR: 12.17, 95% CI: 12.06–12.29).

Conclusions

VS incidence and prevalence are highest among adults and white non-Hispanics. Bilateral VS was more common among children. There was an increase of radiographically confirmed VS over time. A higher proportion of patients received surgical treatment than radiotherapy. Population-based statistics provide healthcare professionals with vital information regarding disease burden and help improve patient care.

Long-Term Outcomes of Sporadic Vestibular Schwannomas Treated with Recent Stereotactic Radiosurgery Techniques

PURPOSE

Vestibular schwannomas (VSs) are benign; thus, understanding long-term tumor control and late adverse radiation effects of stereotactic radiosurgery (SRS) through current radiosurgical techniques is important to inform treatment decisions. Our aim was to clarify long-term tumor control rates and incidence of late adverse radiation effects in patients with VSs followed for 5 years or longer after SRS.

METHODS AND MATERIALS

Altogether, 615 patients with VSs (excluding neurofibromatosis type 2 and partially treated tumors) followed for 5 years or longer after SRS using recent radiosurgical techniques were evaluated. All patients were treated at a margin dose of less than 14 Gy. All tumors were classified into 4 categories: type A (intracanalicular tumor, 87 patients [14%]), type B (cerebellopontine angle [CPA] tumor, 325 patients [53%]), type C (CPA tumor compressing the brain stem, 138 patients [22%]), and type D (CPA tumor compressing the brain stem with a deviation of the fourth ventricle, 65 patients [11%]). Median tumor volume was 2.0 cm³ and median marginal dose was 12 Gy.

RESULTS

Median follow-up period was 158 months. Actuarial 5-, 10-, and 15-year or longer local control (LC) rates were 93%, 91%, and 89%, respectively. Tumor type (P < .001, hazard ratio 2.389) and number of prior surgeries (P = .007, hazard ratio 1.698) were significant for LC. Depending on the tumor type, the actuarial 10-year LC rates were 100%, 93%, 88%, and 70% in type A, B, C, and D tumors, respectively. No patient developed persistent facial palsy. Twenty patients (3.3%) developed delayed cysts. One patient developed malignant transformation (0.2%).

CONCLUSIONS

SRS is a safe and effective treatment for VSs in the long term, excluding VSs compressing the brain stem with a deviation of the fourth ventricle. Delayed cysts such as cyst formation, enlarged preexisting cysts or extratumoral cysts, and malignant transformation should be considered possible causes of long-term treatment failures.

Cystic trigeminal schwannomas

Trigeminal Schwannomas are less than 1% of intracranial tumors, of which only 7% have a cystic component. We documented 2 cases of males with cystic trigeminal Schwannomas, their symptoms, the diagnosis process and the imaging characteristics. In addition, a review of the literature is performed, with emphasis on the radiological classification of this rare entity, that constitutes a diagnostic challenge for the radiologist, who has an essential role in the approach to the disease and therefore in its management.

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.

Long term results of primary radiosurgery for vestibular schwannomas

BACKGROUND

Stereotactic radiosurgery (SRS) has become a primary option for management for both newly diagnosed vestibular schwannomas (VS), as well as VS that enlarge after initial observation.

METHODS

A retrospective review of our prospectively maintained data base found 871 patients who underwent Gamma knife® SRS as their initial (primary) management between 1987 and 2008. Follow-up ranged from 1-25 years (median = 5.2 years) Median tumor volume was 0.9 cc (0.02-36) and median margin dose was 13 Gy (12-25).

RESULTS

Progression free survival (PFS) after SRS was 97% at 3 years, 95% at 5 years, and 94% at 10 years. Freedom from delayed surgical resection was found in 98.7% of patients. Smaller tumor volume was significantly associated with improved PFS. There were 326 patients with serviceable hearing (Gardner-Robertson 1 or 2) at the time of SRS with audiological follow-up of ≥ 1 year. Serviceable hearing preservation rates after SRS were 89.8% at 1 year, 76.9% at 3 years, 68.4% at 5 years, 62.5% at 7 years, and 51.4% at 10 years. Factors associated with improved serviceable hearing preservation included younger age, Gardner-Robertson grade 1 at SRS, and absence of subjective complaints of dysequilibrium or vertigo (vestibulopathy). Fifty-one patients (5.8%) developed trigeminal neuropathy. Fourteen (1.6%) developed a transient House-Brackmann grade 2 or 3 facial neuropathy.

CONCLUSIONS

In this report with extended follow-up, primary SRS achieved tumor growth control in 94% of patients. Optimization of long- term cranial nerve outcomes remains an important achievement of this management strategy for VS.

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.

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.

Hearing preservation after Gamma Knife radiosurgery for cerebellopontine angle meningiomas

OBJECTIVE

The objective of this study was to assess hearing function after Gamma Knife treatment of cerebellopontine angle (CPA) meningiomas and assess factors affecting hearing outcome. Additionally, the authors opted to compare these results with those after Gamma Knife treatment of vestibular schwannomas (VSs), because most of the information on hearing outcome after stereotactic radiosurgery (SRS) comes from reports on VS treatment. Hearing preservation, to the best of the authors’ knowledge, has never been separately addressed in studies involving Gamma Knife radiosurgery (GKRS) for CPA meningiomas.

METHODS

This study included all patients who underwent a single session of GKRS between 2002 and 2014. The patients were divided into two groups. Group A included 66 patients with CPA meningiomas with serviceable hearing and tumor extension into the region centered on the internal auditory meatus. Group B included 144 patients with VSs with serviceable hearing. All patients had serviceable hearing before treatment (Gardner-Robertson [GR] Grades I and II). The median prescription dose was 12 Gy (range 10–12 Gy) in both groups. The median follow-up of groups A and B was 42 months (range 6–149 months) and 49 months (range 6–149 months), respectively.

RESULTS

At the last follow-up, the tumor control rate was 97% and 94% in groups A and B, respectively. Hearing preservation was defined as maintained serviceable hearing according to GR hearing score. The hearing preservation rate was 98% and 66% and the 7-year actuarial serviceable hearing preservation rate was 75% and 56%, respectively, between both groups. In group A, the median maximum cochlear dose in the patients with stable and worsened hearing grade was 6.3 Gy and 5.5 Gy, respectively. In group B, factors affecting hearing preservation were cochlear dose ≤ 7 Gy, follow-up duration, and tumor control. The only determinant of hearing preservation between both groups was tumor type.

CONCLUSIONS

GKRS for CPA meningiomas provides excellent hearing preservation in addition to high tumor control rate. Hearing outcome is better with CPA meningiomas than with VSs. Further long-term prospective studies on determinants of hearing outcome after GKRS for CPA meningiomas should be conducted.

Surgical outcome in smaller symptomatic vestibular schwannomas. Is there a role for surgery?

BACKGROUND

Currently, there is no consensus in the initial management of small vestibular schwannomas (VSs). They are routinely watched and/or referred for radiosurgical treatment, although surgical removal is also an option. We hereby evaluate clinical outcomes of patients who have undergone surgical removal of smaller symptomatic VSs.

METHODS

Patients with vestibular schwannomas (grade T1-T3b according to Hannover classification) were reviewed. Patients with symptomatic tumors who underwent surgery were evaluated. Their preoperative hearing status was based on the guideline of the committee on hearing and equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) foundation. Their postoperative facial nerve function, hearing status, vestibular symptoms, and degree of tumor resection were assessed.

RESULTS

Thirty patients were selected for surgery via a retrosigmoid approach based on their age, symptoms, and their own decision-making after discussion of management options. Most patients presented with hearing loss. Seventeen patients had useful hearing preoperatively. Among them, 10 patients (59%) preserved useful hearing (class A or B) postoperatively. MRI at 1-year follow-up confirmed complete resection in 26/29 patients. Also, 29 patients (97%) had HB grade I-II, and 1 patient had HB III at 1-year follow-up. Except for 1 patient with CSF leak, 1 patient with delayed facial nerve palsy, and 2 patients with asymptomatic sigmoid sinus occlusion, there were no other new morbidities.

CONCLUSION

Although both observation and radiosurgery are valid options in the management of smaller size vestibular schwannomas, surgical treatment seems to offer a high rate of facial nerve preservation, a reasonable rate of hearing sparing, and a high total resection rate. Clinicians should consider surgical treatment as a valid option in the initial management of symptomatic small vestibular schwannomas in younger patients.

Effects of CyberKnife therapy for vestibular schwannoma on hearing: a retrospective study

OBJECTIVES

To evaluate the effects of CyberKnife stereotactic radiotherapy for the treatment of vestibular schwannoma on hearing, as evaluated by audiological tests.

METHODS

Patients with vestibular schwannoma were evaluated before and after CyberKnife radiosurgery. Evaluation included pure tone thresholds, speech discrimination scores, auditory brainstem responses and radiological signs.

RESULTS

The study comprised 26 patients diagnosed with vestibular schwannoma and subsequently treated with CyberKnife radiosurgery. The mean follow-up time was 16.4 months. The mean post-treatment hearing preservation rate was 69.23 per cent. There was no significant relationship between hearing loss after treatment and patient age, radiation dosage during treatment, or size of tumour. With regard to auditory brainstem responses, patients with hearing loss following treatment had a significantly higher inter-peak latency between waves I-III than patients with preserved hearing.

CONCLUSION

Stereotactic CyberKnife radiosurgery is an excellent alternative treatment modality for patients with vestibular schwannoma, and results in acceptable preservation of hearing. Residual hearing following CyberKnife therapy is not significantly affected by factors such as age, size of tumour or dosage of treatment.

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.

Cochlea-sparing acoustic neuroma treatment with 4π radiation therapy

Purpose

This study investigates whether 4π noncoplanar radiation therapy can spare the cochleae and consequently potentially improve hearing preservation in patients with acoustic neuroma who are treated with radiation therapy.

Methods and materials

Clinical radiation therapy plans for 30 patients with acoustic neuroma were included (14 stereotactic radiation surgery [SRS], 6 stereotactic radiation therapy [SRT], and 10 intensity modulated radiation therapy [IMRT]). The 4π plans were created for each patient with 20 optimal beams selected using a greedy column generation method and subsequently recalculated in Eclipse for comparison. Organ-at-risk (OAR) doses, homogeneity index, conformity, and tumor control probability (TCP) were compared. Normal tissue complication probability (NTCP) was calculated for sensorineural hearing loss (SNHL) at 3 and 5 years posttreatment. The dose for each plan was then escalated to achieve 99.5% TCP.

Results

4π significantly reduced the mean dose to both cochleae by 2.0 Gy (32%) for SRS, 3.2 Gy (29%) for SRT, and 10.0 Gy (32%) for IMRT. The maximum dose to both cochleae was also reduced with 4π by 1.6 Gy (20%), 2.2 Gy (15%), and 7.1 Gy (18%) for SRS, SRT, and IMRT plans, respectively. The reductions in mean/maximum brainstem dose with 4π were also statistically significant. Mean doses to other OARs were reduced by 19% to 56% on average. 4π plans had a similar CN and TCP, with a significantly higher average homogeneity index (0.93 vs 0.92) and significantly lower average NTCP for SNHL at both 3 years (30.8% vs 40.8%) and 5 years (43.3% vs 61.7%). An average dose escalation of approximately 116% of the prescription dose achieved 99.5% TCP, which resulted in 32.6% and 43.4% NTCP for SNHL at 3 years and 46.4% and 64.7% at 5 years for 4π and clinical plans, respectively.

Conclusions

Compared with clinical planning methods, optimized 4π radiation therapy enables statistically significant sparing of the cochleae in acoustic neuroma treatment as well as lowering of other OAR doses, potentially reducing the risk of hearing loss.

Hypo-fractionated stereotactic radiotherapy of five fractions with linear accelerator for vestibular schwannomas: A systematic review and meta-analysis

Vestibular schwannomas (VS) are benign tumors stemming from the eighth cranial nerve. Treatment options for VS include conservative management, microsurgery, stereotactic radiosurgery, and fractionated radiotherapy. Though microsurgery has been the standard of care for larger lesions, hypo-fractionated stereotactic radiotherapy (hypo-FSRT) is an emerging modality. However, its clinical efficacy and safety have yet to be established. We conducted a systematic review and meta-analysis of manuscripts indexed in PubMed, Scopus, Web of Science, Embase, and Cochrane databases reporting outcomes of VS cases treated with hypo-FSRT. Five studies representing a total of 228 patients were identified. Across studies, the pooled rates of tumor control, hearing, facial nerve, and trigeminal nerve preservation were 95%, 37%, 97%, and 98%. No instances of malignant induction were observed at median follow-up of 34.8 months. Complications included trigeminal neuropathy (n = 3), maxillary paresthesia (n = 1), neuralgia (n = 1), vestibular dysfunction (n = 1), radionecrosis (n = 1), and hydrocephalus (n = 1). Hypo-FSRT may be another useful approach to manage VS, but studies with extended follow-up times are required to establish long-term safety.

Predictors of hearing outcomes following low-dose stereotactic radiosurgery in patients with vestibular schwannomas: A retrospective cohort review

OBJECTIVES

Hearing deterioration is a major concern for hearing-preserved patients with vestibular schwannomas who are treated with stereotactic radiosurgery (SRS). Thus, determining which patients are more likely to have worse hearing outcomes following SRS may facilitate clinicians in deciding whether conservative policy should be applied in the interest of hearing preservation. This study aimed to define the predictors of hearing outcomes following SRS.

PATIENTS AND METHODS

This retrospective study included 100 patients who underwent low-dose SRS (12- to 13-Gy marginal dose) for vestibular schwannomas between January 2004 and January 2014. Clinical factors and hearing outcomes following radiosurgery were reviewed.

RESULTS

All patients had serviceable hearing at diagnosis and prior to SRS. The median follow-up period was 6.5years (range, 3-10years). The hearing preservation rate in the first, third, and fifth year after radiosurgery was 89%, 68%, and 63%, respectively. A mean cochlear dose lower than 4Gy was a favorable predictor of hearing outcome. Maximal cochlear dose, patient age, pre-treatment pure-tone average, and imaging characteristics were not associated with post-treatment hearing preservation. Our study showed an accelerated rate of deterioration of serial pure-tone average in the first 3years, followed by a more gradual decline after radiosurgery.

CONCLUSION

Our results suggest that cochlear dose constraint is the most crucial factor for hearing preservation. This study provides insight into the rate of hearing preservation and the pattern of hearing deterioration following radiosurgery and can help clinicians advise patients of hearing outcomes following SRS.

Stereotactic radiosurgery vs. fractionated radiotherapy for tumor control in vestibular schwannoma patients: a systematic review

Objective

Repeated controlled studies have revealed that stereotactic radiosurgery is better than microsurgery for patients with vestibular schwannoma (VS) <3 cm in need of intervention. In this systematic review we aimed to compare results from single-fraction stereotactic radiosurgery (SRS) to fractionated stereotactic radiotherapy (FSRT) for patients with VS.

Data sources and eligibility criteria

We systematically searched MEDLINE, Web of Science, Embase and Cochrane and screened relevant articles for references. Publications from 1995 through 2014 with a minimum of 50 adult (>18 years) patients with unilateral VS, followed for a median of >5 years, were eligible for inclusion. After screening titles and abstracts of the 1094 identified articles and systematically reviewing 98 of these articles, 19 were included.

Intervention

Patients with unilateral VS treated with radiosurgery were compared to patients treated with fractionated stereotactic radiotherapy.

Results

No randomized controlled trial (RCT) was identified. None of the identified controlled studies comparing SRS with FSRT were eligible according to the inclusion criteria. Nineteen case series on SRS (n = 17) and FSRT (n = 2) were included in the systematic review. Loss of tumor control necessitating a new VS-targeted intervention was found in an average of 5.0% of the patients treated with SRS and in 4.8% treated with FSRT. Mean deterioration ratio for patients with serviceable hearing before treatment was 49% for SRS and 45% for FSRT, respectively. The risk for facial nerve deterioration was 3.6% for SRS and 11.2% for FSRT and for trigeminal nerve deterioration 6.0% for SRS and 8.4% for FSRT. Since these results were obtained from case series, a regular meta-analysis was not attempted.

Conclusion

SRS and FSRT are both noninvasive treatment alternatives for patients with VS with low rates of treatment failure in need of rescue therapy. In this selection of patients, the progression-free survival rates were on the order of 92–100% for both treatment options. There is a lack of high-quality studies comparing radiation therapy alternatives for patients with VS. Finally, 19 articles reported long-term tumor control after SRS, while only 2 articles reported long-term FSRT results, making effect estimates more uncertain for FSRT.

Electronic supplementary material

The online version of this article (doi:10.1007/s00701-017-3164-6) contains supplementary material, which is available to authorized users.

The Management and Imaging of Vestibular Schwannomas

Vestibular schwannomas are the most common cerebellopontine angle tumor. During the past century, the management goals of vestibular schwannomas have shifted from total resection to functional preservation. Current treatment options include surgical resection, stereotactic radiosurgery, and observation. Imaging has become a crucial part of the initial screening, evaluation, and follow-up assessment of vestibular schwannomas. Recognizing and understanding the management objectives, various treatment modalities, expected posttreatment findings, and complications allows the radiologist to play an essential role in a multidisciplinary team by providing key findings relevant to treatment planning and outcome assessment. The authors provide a comprehensive discussion of the surgical management, role of radiation therapy and observation, imaging differential, and pre- and posttreatment imaging findings of vestibular schwannomas.

Quality of Life in 807 Patients with Vestibular Schwannoma: Comparing Treatment Modalities

Objective In vestibular schwannoma treatment, the choice among treatment modalities is controversial. The first aim of this study was to examine the quality of life of patients with vestibular schwannoma having undergone observation, radiation therapy, or microsurgical resection. The second aim was to examine the relationship between perceived symptoms and quality of life. Last, the association between quality of life and time since treatment was studied. Study Design Cross-sectional study. Setting Tertiary referral center. Subjects and Methods A total of 1208 patients treated for sporadic vestibular schwannoma between 2004 and 2014 were mailed the disease-specific Penn Acoustic Neuroma Quality of Life (PANQOL) questionnaire and additional questions on symptoms associated with vestibular schwannoma. Total and domain scores were calculated and compared among treatment groups. Propensity scores were used, and results were stratified according to tumor size to control for potential confounders. Correlations were calculated to examine the relationship between self-reported symptoms and quality of life, as well as between quality of life and time since treatment. Results Patients with small tumors (≤10 mm) under observation showed a higher PANQOL score when compared with the radiation therapy and microsurgical resection groups. A strong negative correlation was found between self-reported symptoms and quality of life, with balance problems and vertigo having the largest impact. No correlation was found between PANQOL score and time since treatment. Conclusion This study suggests that patients with small vestibular schwannomas experience better quality of life when managed with observation than do patients who have undergone active treatment.

Low-Dose Gamma Knife Radiosurgery for Vestibular Schwannomas: Tumor Control and Cranial Nerve Function Preservation After 11 Gy

OBJECTIVES

This study aims to report tumor control rates and cranial nerve function after low dose (11.0 Gy) Gamma knife radiosurgery (GKRS) in patients with vestibular schwannomas.

METHODS

A retrospective chart review was performed on 30 consecutive patients with vestibular schwannomas treated from March 2004 to August 2010 with GKRS at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. The marginal dose for all patients was 11.0 Gy prescribed to the 50% isodose line. Median follow-up time was 42 months. The median treatment volume was 0.53 cm3. Hearing data were obtained from audiometry reports before and after radiosurgery.

RESULTS

The actuarial progression free survival (PFS) based on freedom from surgery was 100% at 5 years. PFS based on freedom from persistent growth was 91% at 5 years. One patient experienced tumor progression requiring resection at 87 months. Serviceable hearing, defined as Gardner-Robertson score of I-II, was preserved in 50% of patients. On univariate and multivariate analyses, only higher mean and maximum dose to the cochlea significantly decreased the proportion of patients with serviceable hearing.

CONCLUSION

Vestibular schwannomas can be treated with low doses (11.0 Gy) of GKRS with good tumor control and cranial nerve preservation.

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.

Linear accelerator radiosurgery for vestibular schwannomas: Results of medium-term follow-up

BACKGROUND

To examine tumour control, via volume changes, and the complications of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) treatment of vestibular schwannomas (VSs) on medium-term follow-up.

METHODS

Between September 2003 and November 2009 fifty consecutive patients with VSs treated with SRS using a marginal dose of 12.5 Gy utilizing a LINAC equipped with a micro-multileaf collimator were identified. Evaluation included serial magnetic resonance imaging (MRI), and neurological and hearing examinations.

RESULTS

The median tumour volume at treatment was 2.4 (range: 0.24-10.59) cm3. The intracranial diameter of the tumours ranged between 7.7 and 28.7 (median: 15.8) mm. Follow-up MRI was available for analysis on 49 patients. The median radiological follow-up period was 5.8 (range: 1.4-9.2) years. The median tumour volume at last follow-up was 1.1 (range: 0.03-5.3) cm3. VS decreased in size in 45 (90%) patients, with a median reduction in tumour volume of 1.46 (range: 0.06-9.29) cm3 or a median tumour size reduction of 59% of the baseline (range: 6-90%) in these patients. VS remained stable in 2 patients and increased in size in 2 patients. Only 1 patient (2%) required additional intervention (surgery). 15 patients had useful hearing pre-treatment; 10 post-treatment pure-tone audiograms of these patients were available. 5 (50%) patients still had useful hearing post treatment. Non-auditory adverse radiation effects included new (House-Brackmann grade II) or worsened facial nerve palsy (House-Brackmann grade II to grade V) in 2 (4%) patients and trigeminal sensory disturbance in 2 (4%) patients.

CONCLUSIONS

At medium term, the vast majority of VSs treated with LINAC-based SRS exhibit tumour shrinkage. The slightly higher rate of facial nerve palsy compared with Gamma Knife surgery (GKS) results may be related to the learning curve. Other complications were similar to reported GKS results for VSs of comparable sizes.

Management of sporadic vestibular schwannoma

Vestibular schwannomas (VS) comprise 8% of all intracranial tumors and 90% of cerebellopontine angle and internal auditory canal neoplasms. Secondary to the widespread adoption of screening protocols for asymmetrical hearing loss and the increasing use of advanced imaging, the number of VS diagnosed each year continues to rise, while the average size has declined. Microsurgery remains the treatment of choice for large tumors, however the management of small- to medium-sized VS remains highly controversial with options including observation, radiotherapy, or microsurgery. Within this chapter, the authors provide an overview of the contemporary management of VS, reviewing important considerations and common controversies.

Clinical evaluation of CyberKnife in the treatment of vestibular schwannomas

Objective. This study assessed the posttreatment tumor control and auditory function of vestibular schwannoma (VS) patients after CyberKnife (CK) and analyzed the possible prognostic factors of hearing loss. Methods. We retrospectively studied 117 VS patients, with Gardner-Robertson (GR) classification grades I to IV, who underwent CK between 2006 and 2012. Data including radiosurgery treatment parameters, pre- and postoperative tumor size, and auditory function were collected and examined. Results. With CK, 117 patients had excellent tumor control rates (99.1%), with a mean imaging followup of 61.1 months. Excluding 52 patients (GR III-IV pretreatment), 53 (81.5%) of the remaining 65 patients (initial GR I-II) maintained GR I or II hearing after CK, with a mean audiometric followup of 64.5 months. Twelve patients experienced hearing degradation (91.6% were GR II pretreatment); they appeared to have significantly larger tumor sizes, significantly smaller cochlear sizes, and higher prescribed cochlear doses, compared to the patients with preserved hearing. Conclusion. Our data showed that CK treatment provided an excellent tumor control rate and a comparable hearing preservation rate in VS patients. Patients with pretreatment GR II hearing levels, larger tumor volumes, smaller cochlear sizes, and higher prescribed cochlear doses may have poor hearing prognoses.

Long-term hearing outcomes following stereotactic radiosurgery for vestibular schwannoma: patterns of hearing loss and variables influencing audiometric decline

Object

The goals of this retrospective cohort study were as follows: 1) to describe the long-term prevalence and timing of hearing deterioration following low-dose (12- to 13-Gy marginal dose) stereotactic radiosurgery (SRS) for vestibular schwannoma (VS); and 2) to identify clinical variables associated with long-term preservation of useful hearing following treatment.

Methods

Patients with serviceable hearing who underwent SRS for VS between 1997 and 2002 were studied. Data including radiosurgery treatment plans, tumor characteristics, pre- and posttreatment pure tone average, speech discrimination scores, and American Academy of Otolaryngology–Head and Neck Surgery hearing class were collected. Time to nonserviceable hearing was estimated using the Kaplan-Meier method. Univariate and multivariate associations with time to nonserviceable hearing were evaluated using Cox proportional hazards regression models.

Results

Forty-four patients met the study criteria and were included. The median duration of audiometric follow-up was 9.3 years. Thirty-six patients developed nonserviceable hearing at a mean of 4.2 years following SRS. The Kaplan-Meier estimated rates of serviceable hearing at 1, 3, 5, 7, and 10 years following SRS were 80%, 55%, 48%, 38%, and 23%, respectively. Multivariate analysis revealed that pretreatment ipsilateral pure tone average (p < 0.001) and tumor size (p = 0.009) were statistically significantly associated with time to nonserviceable hearing.

Conclusions

Durable hearing preservation a decade after low-dose SRS for VS occurs in less than one-fourth of patients. Variables including preoperative hearing capacity and tumor size may be used to predict hearing outcomes following treatment. These findings may assist in pretreatment risk disclosure. Furthermore, these data demonstrate the importance of long-term follow-up when reporting audiometric outcomes following SRS for VS.

Hearing preservation after radiotherapy for vestibular schwannomas is comparable to hearing deterioration in healthy adults and is accompanied by local tumor control and a highly preserved quality of life (QOL) as patients' self-reported outcome

PURPOSE

To evaluate long-term results and patients' self-reported outcome of high-precision photon radiotherapy for the treatment of patients with vestibular schwannoma (VS).

METHODS AND MATERIALS

We treated 246 patients with 248 VS with fractionated stereotactic radiotherapy (FSRT) or stereotactic radiosurgery (SRS). For FSRT, a median total dose of 57.6 Gy was prescribed in median single doses of 1.8 Gy, for SRS, a median dose of 13 Gy/80% isodose was applied. Of all patients, 51 patients died during follow-up. To evaluate long-term toxicity and QOL, we sent out a questionnaire to all living patients; of these, 81 patients (42%) sent back the questionnaire.

RESULTS

Median local control was 84 months, actuarial local control rates for both groups (SRS and FSRT) were 98% after 2, 95% after 5, and 93% after 10 years; there was no statistical difference between FSRT and SRS. Hearing deterioration was significantly higher in the SRS group than the FSRT group. However, when comparing FSRT to SRS with doses ≤ 13 Gy, hearing preservation is comparable. In patients with useful hearing, hearing preservation was 89.7% at 1 year, 84.7% at 3 years, 76.5% at 5 years, and 68.6% at 10 years. After 10 years of follow-up, hearing deterioration can be observed in both subgroups. In the FSRT group, facial nerve toxicity rate was 1.6%. Trigeminal nerve toxicity was observed in 2.1% after FSRT. Overall QOL was unchanged in 47% of the patients after RT, and 31% reported an improvement in QOL during follow-up.

CONCLUSION

Patients' self-reported outcome confirms good results with respect to tumor control and QOL after FSRT or SRS in patients with VS. SRS can be associated with higher side effect following a dose-dependency. In long-term follow-up, hearing deterioration is most likely attributed to normal aging, but not treatment-related.