Stereotactic radiosurgery for vestibular schwannomas

Individual- and Community-Level Social Determinant Associations With Acoustic Neuroma Disparities in the United States

OBJECTIVE

This investigation aims to determine whether community-level social determinants of health (SDoH) influenced acoustic neuroma outcomes more profoundly than individual-level SDoH through the use of multivariate models and census-level socioeconomic status (SES) measures.

STUDY DESIGN

Observational, retrospective cohort study. Setting: Specially Authorized Head-Neck SEER 2020 Dataset.

PATIENTS

23,330 adult (20+ yr) patients diagnosed with acoustic neuroma from 2010 to 2018.

MAIN OUTCOME MEASURES

Age-adjusted multivariate regressions and hazard models were performed for individual level (sex, race-ethnicity) and community-level factors (Yost Index-SES, rurality-urbanicity) to assess for differences in acoustic neuroma treatment, including delay of intervention, treatment receipt, and overall survival.

RESULTS

Lower Yost-SES/community-level SES had a markedly positive association with an increase in all-cause mortality (HR, 1.55; 95% CI, 1.41-1.71) and negative association with stereotactic radiotherapy treatment (OR, 0.93; 95% CI, 0.86-0.99; p = 0.040). Patients with poor Yost-SES had a significantly positive association with receipt of surgical resection (OR, 1.13; 95% CI, 1.07-1.20; p < 0.001).

CONCLUSIONS

Data generated from this investigation suggest that community-level SDoH, particularly Yost-SES, have more detrimental care and prognostic disparities in acoustic neuroma treatment compared with individual-level factors.

Risk analysis of radiosurgery for vestibular schwannoma: Systematic review and comparative study of 10-year outcomes

Background

Determine the benefit of stereotactic radiosurgery (SRS) compared to no treatment for sporadic vestibular schwannoma (VS) by calculating epidemiologic risk using 10-year data; apply the analysis to VS that have demonstrated linear growth.

Methods

PubMed, Google Scholar, Web of Science, and Cochrane Library are systematically reviewed for VS tumor control 10 years after SRS and compared to a historical cohort of untreated VS (primary risk analysis). Subgroups of VS limited by size and observed growth are compared to the untreated cohort (secondary analysis).

Results

Twenty-four studies of 4079 SRS-treated VS exhibited tumor control in 90.93% (87.0%-100%; SD 4.1%), while 1959 untreated VS exhibited control in 65.24%. SRS reduces the absolute risk (ARR) of tumor progression by 25.7% compared to no treatment. The number needed to treat (NNT) is 4 (3.892, 95% CI: 3.619-4.210). Subgroup analyses of (1) VS with definite linear growth before SRS result in a similar ARR of 29.4% and NNT 4 (3.395, 95% CI: 2.966-3.968), and (2) Koos 1 VS result in lower ARR 18.31% and higher NNT 6 (5.209; 95% CI: 4.018-7.401).

Conclusions

This "best-available" case-control study of 10-year data reveals that ARR and NNT are similar for VS with and without definite pretreatment linear growth. These comparisons may be applied to CPA diameters less than 2 cm. Results for Koos 1 tumors are different. This analysis quantifies the therapeutic benefit of SRS by comparative risk analysis. The level of evidence on this topic is low.

Initial Experience of Implementing a Pre-treatment Dry Run for HyperArc Stereotactic Radiosurgery Treatments With Optical Surface Imaging for Intra-fraction Motion Monitoring

Linac-based stereotactic radiosurgery (SRS) with planning target volume (PTV) margins <1 mm has become increasingly common in recent years. Optical surface imaging for surface-guided radiation therapy (SGRT) is often used for intra-fraction motion monitoring during these treatments to facilitate the use of a smaller PTV margin by providing real-time quantitative patient positioning information. However, rotating the couch introduces errors to SGRT-reported translations and rotations that can be problematic for SRS treatments with non-coplanar arcs and very small PTV margins. This work presents a novel approach for decreasing the magnitude of these errors by performing a pre-treatment dry run and capturing reference surfaces with the SGRT system at each couch angle included in the treatment plan. Time from cone beam computed tomography (CBCT) to treatment initiation and total treatment session time were reviewed for 30 single-fraction brain SRS cases treated using this technique to determine the effect of including the dry run on treatment session times. Out of the 30 cases treated between April 2023 and January 2024, 23 treatments required only a single CBCT prior to treatment, with no additional mid-treatment imaging required to verify patient positioning after motion. The median time between CBCT and treatment initiation was 7.98 minutes (interquartile range (IQR) = 7.28 to 8.93 minutes). The median time from CBCT to treatment completion was 15.43 minutes (IQR = 13.67 to 21.97 minutes). In the six patients that required one additional CBCT, the treatment session times ranged from 24.32 to 32.83 minutes. There was one patient who required three mid-treatment CBCTs, and the treatment session time was 67.87 minutes. Incorporating the pre-treatment dry run with the acquisition of reference surfaces at each treatment angle decreased errors in SGRT-reported translations and rotations associated with couch rotation without significantly increasing treatment session times.

Managing vestibular schwannomas with radiosurgery and radiotherapy: AGREE II appraisal of clinical practice guidelines

INTRODUCTION

Vestibular schwannomas (VSs) are rare, benign intracranial tumours that have prompted clinical practice guideline (CPG) creation given their complex management. Our aim was to utilize the Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument to assess if such CPGs on the management of VSs with radiosurgery and radiotherapy are of acceptable quality.

METHODS

Relevant CPGs were identified following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocols. Experienced reviewers then extracted general CPG properties and rated their quality via the AGREE II instrument. Intraclass correlation coefficients (ICCs) were quantified to assess interrater reliability.

RESULTS

Nine CPGs on the management of VSs with radiosurgery and radiotherapy were identified. All CPGs were created in the past six years and developed recommendations based on literature review and expert consensus. One guideline was deemed as high quality with seven others being moderate and one being low in quality. The clarity of the presentation domain had the highest mean scaled domain score of 96.0%. The domains of stakeholder involvement and applicability had the lowest means of 49.2% and 47.2%, respectively. ICCs were either good or excellent across all domains.

CONCLUSION

Current CPGs on the management of VSs with radiosurgery and radiotherapy are of acceptable quality but would greatly benefit from improvements in applicability, stakeholder involvement, editorial independence and rigour of development. We recommend CPG authors reference the European Association of Neuro-Oncology (EANO) guideline as a developmental framework with the Congress of Neurological Surgeons/American Association of Neurological Surgeons (CNS/AANS) CPG being a valid alternative.

Homogenous dose prescription in Gamma Knife Radiotherapy: Combining the best of both worlds

PURPOSE

Stereotactic radiosurgery with linear accelerators (LINACs) or Leksell Gamma Knife® (LGK, Elekta AB) is an established treatment option for intracranial tumors. When those are involving/abutting organs at risk (OAR), homogenous and normofractionated treatments outmatch single fraction deliveries. In such situations, it would be desirable to balance LINAC's homogeneity benefits with LGK's dose gradient attributes. In this study, we determined homogeneity and OAR sparing ranges using a non-clinical, homogenous prototype version of LGK Lightning.

METHODS

We retrospectively analyzed thirty fractionated LGK Icon in-house patients with acoustic neuromas, pituitary adenomas and meningiomas. Four treatment plans were generated (54 Gy,1.8 Gy/fx) per patient: one LINAC plan, one clinical Lightning plan ("LGK") and two prototype Lightning plans ("LGK Hom" and "LGK OAR"). We analyzed Dmean and D2% for different OAR, Gradient Index (GI), Paddick Conformity Index (PCI), Homogeneity Index (HI) and beam-on-time (BOT).

RESULTS

While the LINAC vs. Lightning plans (LGK Hom|LGK OAR|LGK) boast better homogeneity (median: 1.08 vs. 1.18|1.24|1.35) and shorter BOT (median: 137 s vs. 432 s|510 s|510 s), Lightning plans show improved GI (median: 6.68 vs. 3.86|3.50|3.19), similar PCI (median: 0.75 vs. 0.76|0.75|0.82) and significantly reduced OAR doses. For in-tumor OAR, LGK Hom and LINAC plans achieves similar OAR sparing with improved GI for LGK Hom.

CONCLUSIONS

This study is a preliminary attempt to combine the dosimetric advantages of LINAC and LGK treatment planning. We observed that LGK plan homogeneity can be improved toward LINAC standards while maintaining the LGK advantage of favorable OAR doses and GI. Additionally, in-tumor OAR hotspots can be considerably reduced.

The impact of artificial intelligence in the diagnosis and management of acoustic neuroma: A systematic review

BACKGROUND

Schwann cell sheaths are the source of benign, slowly expanding tumours known as acoustic neuromas (AN). The diagnostic and treatment approaches for AN must be patient-centered, taking into account unique factors and preferences.

OBJECTIVE

The purpose of this study is to investigate how machine learning and artificial intelligence (AI) can revolutionise AN management and diagnostic procedures.

METHODS

A thorough systematic review that included peer-reviewed material from public databases was carried out. Publications on AN, AI, and deep learning up until December 2023 were included in the review's purview.

RESULTS

Based on our analysis, AI models for volume estimation, segmentation, tumour type differentiation, and separation from healthy tissues have been developed successfully. Developments in computational biology imply that AI can be used effectively in a variety of fields, including quality of life evaluations, monitoring, robotic-assisted surgery, feature extraction, radiomics, image analysis, clinical decision support systems, and treatment planning.

CONCLUSION

For better AN diagnosis and treatment, a variety of imaging modalities require the development of strong, flexible AI models that can handle heterogeneous imaging data. Subsequent investigations ought to concentrate on reproducing findings in order to standardise AI approaches, which could transform their use in medical environments.

Cochlear radiation dose and hearing loss in patients with vestibular schwannoma undergoing radiosurgery: systematic review

OBJECTIVES

To determine the cut-off point of the cochlear radiation dose as a risk factor for hearing loss in patients with vestibular schwannoma treated with radiosurgery.

METHODS

A systematic review of the literature was performed without language or publication year restrictions in the MEDLINE/PubMed, EMBASE, Web of Science, LILACS/VHL and Cochrane Library databases. Studies that met the following criteria were included: 1) population: adults of both sexes who underwent radiosurgery for vestibular schwannoma treatment; 2) exposure: cochlear radiation; 3) outcome: hearing loss; 4) type of study: cohort. Two independent reviewers conducted the entire review process. The registration number in PROSPERO was CRD42020206128.

RESULTS

From the 333 articles identified in the searches, seven were included after applying the eligibility criteria. There was no standardization as to how to measure exposure or outcome in the included studies, and most studies did not present sufficient data to enable meta-analysis.

CONCLUSION

It was not possible to determine a cut-off point for high cochlear dose that could be considered a risk factor for hearing loss.

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.

Subclassification of the Koos grade 2 vestibular schwannoma into 2a and 2b for individualized patient care: a validity and reliability study

OBJECTIVE

Vestibular schwannoma (VS) growth of ≥2 mm during serial MRI observation, irrespective of size, is the benchmark for treatment initiation in almost all centers. Although the probability of less optimal outcomes significantly increases in VS closer to the brainstem, early intervention does not improve long-term quality of life. Moving beyond the recommendation of definitive treatment for all VS after detected growth, we subclassified Koos 2 tumors based on extrameatal extension and relation to the brainstem. The aim of the current study was to evaluate the Koos 2 subclassification's validity and the inter-and intra-rater reliability of the entire Koos classification.

METHODS

Six experts, including neurosurgeons, otorhinolaryngologists and radiologists from two tertiary referral centers, classified 43 VS MRI scans. Validity of the Koos 2 subclassification was evaluated by the percentage agreement against the multidisciplinary skull base tumor board management advice. Inter- and intra-rater reliability were calculated using the intraclass correlation coefficient (ICC).

RESULTS

Validity was almost perfect in Koos 2a VSs with a 100% agreement and 87.5% agreement for Koos 2b. Inter-rater reliability for all Koos grades was significantly excellent (ICC 0.91; 95%CI 0.866 to 0.944, p= <0.001). Five raters had an excellent intra-rater reliability (ICC > 0.90; p= <0.01) and one rater had a good intra-rater reliability (ICC 0.88; 95% CI 0.742 to 0.949).

CONCLUSIONS

Although multiple factors influence decision-making, the classification of Koos 2a and 2b with excellent inter- and intra-rater reliability, can aid in recommending treatment initiation, moving beyond detected tumor growth, aiming to optimize patient centered care.

A bibliometric and visualization analysis of global research on vestibular schwannoma

BACKGROUND

Vestibular schwannoma is the most common benign tumor in the pontocerebellar horn region. As the tumor grows, it often causes severe hearing loss due to compression of nearby nerves, resulting in a lower quality of life. This study examined vestibular schwannoma-related research through a bibliometric and visualization analysis, and it explored current trends and research hot spots.

METHODS

Research related to vestibular schwannoma published from 2002 to 2021 was searched using the Web of Science Core Collection. The processing and visualization analysis of the data were conducted using R software, VOSviewer, and CiteSpace.

RESULTS

A total of 3,909 publications were included in this study, and an overall increasing trend in the annual output of publications was found. The United States, Germany, and the United Kingdom were the most prolific countries, publishing the most articles. Germany had the most frequent international cooperation and the highest centrality score. The Mayo Clinic, University of California, and Harvard University were the three most productive institutions. Otology & Neurotology was the most prolific journal, and MJ Link was the most productive and highest scoring author for centrality. Current frontier topics mainly focused on "hearing preservation" and "radiosurgery". A map of trends in topics and a thematic graph revealed that "hearing loss", "vertigo", "magnetic resonance imaging", "radiosurgery", "stereotactic radiosurgery", and "gamma knife" were the topics of focus of current discussions.

CONCLUSION

Hearing preservation is a current frontier topic in this area. Radiosurgery has a promising future in the field of vestibular schwannoma, and stereotactic radiosurgery is a focus of global attention. Bibliometric and visualization analysis offer a unique and objective perspective of the field of vestibular schwannoma and may assist scholars in the identification of new research directions.

Impact of Social Determinants of Health on Stereotactic Radiotherapy for Vestibular Schwannoma

OBJECTIVES/HYPOTHESIS

Linear accelerator (LINAC) and Gamma Knife (GK) are common stereotactic radiation therapies for treating vestibular schwannoma (VS). There is currently limited literature examining specific demographic and socioeconomic factors, which influence the type of stereotactic radiation therapy a patient with VS receives.

STUDY DESIGN

Retrospective database review.

METHODS

The National Cancer Database was queried for cases of VS between 2004 and 2016. Patient demographic characteristics were compared using chi-squared and t-tests between GK and LINAC treated groups. Multivariate regression analysis was performed to assess predictors of stereotactic radiation therapy received.

RESULTS

Of the 6,208 included patients, 5,306 (85.5%) received GK and 902 (14.5%) received LINAC. The mean age of GK patients was significantly lower than that of LINAC patients (58.0 vs. 59.7, P < .001). Individuals treated with GK had greater proportions of private insurance (P < .001) and incomes greater than $63,332 (P = .003). A greater proportion of GK patients were treated in academic centers (P < .001), in high-volume facilities (P < .001), in metropolitan areas (P < .001), and in the Northeastern United States (P < .001). On multivariate logistic regression analysis, region, metropolitan area, facility type, tumor size, and distance traveled by patients independently predict receipt of GK versus LINAC.

CONCLUSION

Differences in patient demographics and other social determinants of health influence choice of GK versus LINAC therapy for VS patients. Future studies focused on addressing barriers to care, which may influence postprocedural quality of life and clinical outcomes associated with these two treatments are necessary to better understand the impact of these social differences.

LEVEL OF EVIDENCE

4 Laryngoscope, 2022.

Technical note: A spiral fluid-attenuated inversion recovery magnetic resonance imaging technique for stereotactic radiosurgery treatment planning for trigeminal neuralgia

PURPOSE

Magnetic resonance imaging (MRI) is commonly used in treatment planning for stereotactic radiosurgery (SRS) of trigeminal neuralgia (TN). With current MRI techniques, the delineation of the trigeminal nerve root entry zone (REZ) may be degraded due to poor contrast and artifacts. The purpose of this work is to develop an MRI technique with better delineation of the trigeminal nerve REZ to improve SRS treatment planning for TN.

METHODS

A spiral fluid-attenuated inversion recovery (FLAIR) MRI technique was developed to improve image quality by improving tissue contrast, fluid suppression, artifact reduction, and signal-to-noise ratio (SNR). A concomitant-phase compensation method based on spiral gradient waveforms was implemented to minimize artifacts due to magnetic field change induced by the metal frame used in Gamma Knife treatment planning. The image quality of spiral FLAIR was assessed in four healthy volunteers. The geometric accuracy was quantitatively evaluated by registering spiral FLAIR to computed tomography (CT) images and comparing it with existing MRI techniques.

RESULTS

The spiral FLAIR technique demonstrated better delineation of the trigeminal nerve REZ, improved tissue contrast of the brain stem, and minimized flow artifacts, compared to steady-state free precession (SSFP) MRI. Spiral FLAIR also improved fluid suppression, SNR, and artifacts, which contributed to better delineation of the trigeminal nerve REZ compared to conventional Cartesian FLAIR. The measured mean (± standard deviation) distance between spiral FLAIR and CT images is 0.98 ± 0.56 mm, comparable to 0.40 ± 0.26 mm in 3T T1 spoiled gradient echo (T1-SPGR), 0.59 ± 0.25 mm in 3T SSFP, 0.66 ± 0.38 mm in 1.5T T1-SPGR, and 0.61 ± 0.25 mm in 1.5T Cartesian FLAIR.

CONCLUSION

A spiral FLAIR technique with improved image quality and good geometric accuracy provides a potential alternative for treatment planning in SRS for TN patients.

The Role of Magnetic Resonance Imaging (MRI) in Diagnostics of Acoustic Schwannoma

Background:

Acoustic neuromas are also called vestibular schwannoma, acoustic neurinoma, vestibular neuroma, and acoustic neurofibroma. These are tumors that evolve from Schwann cell sheath and can be either intracranial or extra-axial. They usually occur adjacent to the cochlear or vestibular nerve. Anatomically, acoustic neuromas tend to occupy the cerebellopontine angle. About 20% of internal carotid artery (ICA) tumors are meningiomas and may occur elsewhere in the brain. Bilateral acoustic neuromas also tend to be exclusively in individuals with type 2 neurofibromatosis.

Objective:

The aim was to asses the role of MRI in evaluation of cerebellopontine angle acoustic schwannomas, the role of the cyber knife treatment in eliminating the tumor with a maximum protection of healthy tissue.

Methods:

MRI, GE 1.5 Tesla unit and standard protocol: Pre-contrast MRI images of the temporal bones and posterior fossa were obtained using Ax 3D Fiesta T2W Hi-resolution; Ax 3D T1 Fat-Suppressed, Thin-slice (2mm) Coronal T2W, Sag 3D FiestaT2W Hi-resolution images. Post-contrast images were obtained using Ax 3D T1 Fat-Suppressed Cor 3D T1 Fat-suppressed sequences. FLAIR sequence axial).

Case report:

A woman 62 years of age, reported sudden tinnitus, dizziness, hearing loss in her left ear. After one years she began to experience vertigo, headache.

Results:

MRI of brain temporal bone with contrast show acoustic schwannoma measuring 20x9 mm on the left cerebellopontine angle extending into and enlarging the left IAC, solid enhancing component is seen the acoustic meatus and peripheral contrast cystic component in the left cerebellopontine angle, after cyber knife treatment MRI result was the solid component of the mass, filling the left internal acoustic canal shows marked post-contrast enhancement and is measured 10x5x4mm, cystic component of it filling the left cerebellopontine angle cistern is enlarged to 25x19x12mm), it extends down till the left lateral aspect of medullary cistern, abutting the CN-XII at its entrance to left hypoglossal canal. After 5 month control show, a 15mm long and 5mm thick neoplastic soft-tissue in the left internal acoustic canal, with post-contrast enhancement, measured up to 12mm at the level of porus acusticus but cystic component of the mass in left cerebellopontine angle cistern is no longer visible in this MRI exam.

Conclusion:

The sensitivity of MRI for correctly diagnosing acoustic schwannoma was 100 % and specificity was 92.86 % with a positive predictive value of 94.12 % and accuracy of 96.67 %. MRI is considered as an excellent noninvasive investigation for pontocerebral angle Schwannoma’s.

Clinical outcomes of fractionated stereotactic radiosurgery in treating perioptic meningiomas and schwannomas: A single-institutional experience

Application of radiosurgery to the newly diagnosed or post-operative residual perioptic lesions has been proved to improve tumor control. However, risk of vision injury induced by radiosurgery may increase substantially if the radiation dose is too high or tumor is close to the optic apparatus. The purpose of this study was to evaluate the safety and the effectiveness of fractionated stereotactic radiosurgery (FSRS) for perioptic tumors. We retrospectively analyzed 60 consecutive patients with 53 meningiomas and 7 schwannomas treated with FSRS between October 2007 and February 2020. We administered a marginal dose of 6-7 Gy (mean 6.8 Gy) per fraction and delivered 3 fractions in 3 consecutive days. The median tumor volume was 6.31 cm³ (range 0.3-58.23 cm³). The mean minimum lesion-optic distance (MLOD) is 0.85 mm (range 0-3 mm). After mean follow-up period of 69.6 months (range 6.82-156.32 months; median 58.9 months), the tumor control rates at 1, 3, 5, 8 and 13 years were 98.3%, 93.4%, 90.60%, 88.4% and 88.4%, respectively. Four out of the 60 tumors (6.7%) experienced a transient volume increase after FSRS. None of the patients developed visual impairment related to radiation induced optic neuropathy (RION) after FSRS. In conclusion, FSRS offers an alternative treatment option in treating perioptic meningiomas and schwannomas with acceptable tumor control rates and good visual preservation in the present study.

Near Total Versus Gross Total Resection of Large Vestibular Schwannomas: Facial Nerve Outcome

BACKGROUND

Large vestibular schwannomas (VSs) with brainstem compression are generally reserved for surgical resection. Surgical aggressiveness must be balanced with morbidity from cranial nerve injury. The purpose of the present investigation is to evaluate the clinical presentation, management modality, and patient outcomes following near total resection (NTR) vs gross total resection (GTR) of large VSs.

OBJECTIVE

To assess facial nerve outcome differences between GTR and NTR patient cohorts.

METHODS

Between January 2010 and March 2018, a retrospective chart review was completed to capture patients continuously who had VSs with Hannover grades T4a and T4b. NTR was decided upon intraoperatively. Primary data points were collected, including preoperative symptoms, tumor size, extent of resection, and postoperative neurological outcome.

RESULTS

A total of 37 patients underwent surgery for treatment of large and giant (grade 4a and 4b) VSs. Facial nerve integrity was preserved in 36 patients (97%) at the completion of surgery. A total of 27 patients underwent complete resection, and 10 had near total (>95%) resection. Among patients with GTR, 78% (21/27) had House-Brackmann (HB) grade I-II facial nerve function at follow-up, whereas 100% (10/10) of the group with NTR had HB grade I-II facial nerve function. Risk of meningitis, cerebrospinal fluid leak, and sinus thromboses were not statistically different between the 2 groups. There was no stroke, brainstem injury, or death. The mean follow-up was 36 mo.

CONCLUSION

NTR seems to offer a benefit in terms of facial nerve functional outcome compared to GTR in surgical management of large VSs without significant risk of recurrence.

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.

Individualized automated planning for dose bath reduction in robotic radiosurgery for benign tumors

Object

To explore the use of automated planning in robotic radiosurgery of benign vestibular schwannoma (VS) tumors for dose reduction outside the planning target volume (PTV) to potentially reduce risk of secondary tumor induction.

Methods

A system for automated planning (AUTOplans) for VS patients was set up. The goal of AUTO- planning was to reduce the dose bath, including the occurrence of high dose spikes leaking from the PTV into normal tissues, without worsening PTV coverage, OAR doses, or treatment time. For 20 VS patients treated with 1x12 Gy, the AUTOplan was compared with the plan generated with conventional, manual trial-and-error planning (MANplan).

Results

With equal PTV coverage, AUTOplans showed clinically negligible differences with MANplans in OAR sparing (largest mean difference for all OARs: ΔD2% = 0.2 Gy). AUTOplan dose distributions were more compact: mean/maximum reductions of 23.6/53.8% and 9.6/28.5% in patient volumes receiving more than 1 or 6 Gy, respectively (p<0.001). AUTOplans also showed smaller dose spikes with mean/maximum reductions of 22.8/37.2% and 14.2/40.4% in D2% for shells at 1 and 7 cm distance from the PTV, respectively (p<0.001).

Conclusion

Automated planning for benign VS tumors highly outperformed manual planning with respect to the dose bath outside the PTV, without deteriorating PTV coverage or OAR sparing, or significantly increasing treatment time.