Macrophage Density Predicts Facial Nerve Outcome and Tumor Growth after Subtotal Resection of Vestibular Schwannoma

Immune Profiling of Secreted Factors from Human Vestibular Schwannoma Cells and Tumor-associated Macrophages

OBJECTIVES

This study compared the immune-related secretory capacity of human vestibular schwannoma (VS) and tumor-assisted macrophages (TAMs) with their normal counterparts (Schwann cells [SC] and peripheral blood monocyte-derived macrophages [Mo-MFs], respectively), and examined relationships with presurgical hearing and tumor size.

METHODS

VS tumors (n = 16), auditory nerve (n = 1), blood (n = 9), and great auricular nerves (n = 3) were used. SCs (S100B+ ) and TAMs (CD68+ ) were isolated from VS tissue for culture. The secreted levels of 65 immune-related factors were measured and compared using unpaired t-tests with Welch correction (schwannoma vs. SCs) or Mann-Whitney tests (TAMs and Mo-MFs). Associations between factor concentration and word recognition (WR), pure-tone average (PTA), and tumor size were evaluated with Spearman correlation.

RESULTS

Secreted factors with significantly higher concentrations in schwannoma versus SC supernatants included IL-2 and BAFF, whereas MMP-1, IL-6, FGF-2, VEGF-A, MIP-3α, and GRO-α concentrations were significantly higher in TAMs versus Mo-MFs (all p < 0.05). Worse WR was significantly associated with higher secretion of fractalkine, eotaxin-3, CD30, and IL-16 by VS cells; IP-10, eotaxin-3, multiple interleukins, GM-CSF, SCF, and CD30 by TAMs; and TNF-α and MIP-1α by Mo-MFs (all p < 0.05). Worse PTA was significantly correlated with higher secretion of IL-16 by VS cells (p < 0.05). Larger tumor size was significantly correlated with higher secretion of eotaxin by VS cells, and of IL-7, IL-21, and LIF by TAMs (all p = 0.017).

CONCLUSIONS

Differential secretion of immune-related factors was observed in schwannoma versus normal SCs and in TAMs versus Mo-MFs, some of which were correlated with worse hearing and larger VS tumors.

LEVEL OF EVIDENCE

N/A Laryngoscope, 134:S1-S14, 2024.

Identifying Tumor Microenvironment Biomarkers in Adherent and Cystic Vestibular Schwannomas

OBJECTIVE

A subset of vestibular schwannomas (VSs), including cystic tumors, have higher postoperative morbidity because of the presence of adhesions between the tumor, facial nerve (FN), and brainstem. We identify tumor microenvironment (TME) biomarkers to better classify these tumors and predict the degree of tumor adherence.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary skull base referral center.

METHODS

Adult patients with cystic and solid VS matched in tumor size who underwent surgical resection were included. Expressions of seven biomarkers of extracellular matrix remodeling and tumor immune response were quantified via immunohistochemistry. The distribution of CD45+ immune cells was evaluated in intratumoral and perivascular compartments. The degree of tumor adherence was categorized as none, adherent to FN, or adherent to both FN and brainstem.

RESULTS

Twenty-eight patients were included. Cystic VSs were significantly more adherent than solid VSs ( p = 0.02). Patients with adherent VS had shorter duration of symptoms and were more likely to undergo subtotal resection. In solid tumors, matrix metalloproteinase (MMP)-2 expression ( p = 0.02) and CD163+ macrophage infiltration ( p = 0.007) were correlated with tumor size. Linear discriminant analyses (LDAs) demonstrated MMP-2, MMP-14, CD80, CD163, and perivascular CD45 to be individually predictive of the degree of tumor adherence (all p < 0.05), with perivascular CD45 being the best independent predictor ( p = 0.005). An LDA model including these biomarkers demonstrated 100% accurate discrimination of all three levels of tumor adherence ( p = 0.04).

CONCLUSIONS

Adherent VS have a distinct proinflammatory TME characterized by elevated MMP expression, enrichment of tumor-associated macrophages, and perivascular immune cell infiltration.

Comparison of Postoperative Outcomes in Cystic Versus Solid Vestibular Schwannoma in a Multi-institutional Cohort

OBJECTIVE

Cystic vestibular schwannomas (cVSs) have more variable and less favorable clinical outcomes after microsurgical resection compared with solid VS (sVS). This study compares the preoperative presentation and postoperative outcomes between cVS and sVS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Two tertiary skull base referral centers.

METHODS

Consecutive adult patients who underwent VS resection from 2016 to 2021 were included. Univariate and multivariate analyses compared differences in baseline symptoms and postoperative outcomes between cVS and sVS.

RESULTS

There were a total of 315 patients (64% female; mean age, 54 yrs) and 46 (15%) were cystic. cVS were significantly larger than sVS (maximum diameter, 28 vs. 18 mm, p < 0.001) and had higher rates of dysphagia and dysphonia preoperatively (p < 0.02). cVSs were more likely to undergo translabyrinthine resection (76 vs. 50%, p = 0.001) and have a higher rate of subtotal resection (STR) compared with sVS (30 vs. 13%, p = 0.003). At latest follow-up, fewer cVS achieved good facial nerve (FN) outcome (House-Brackmann [HB] I/II) (80 vs. 90%, p = 0.048). Subanalysis of cVS and sVS matched in tumor size, and surgical approach did not show differences in the rate of STR or FN outcomes (HB I/II, 82 vs. 78%, p = 0.79).

CONCLUSION

In this large multi-institutional series, cVSs represent a distinct entity and are characterized by larger tumor size and higher incidence of atypical symptoms. Although cVSs were more likely to undergo STR and portend worse FN outcomes than sVSs, this may be due to their larger tumor size rather than the presence of the cystic component.

Cytokine Profiling of Cyst Fluid and Tumor-Associated Macrophages in Cystic Vestibular Schwannoma

BACKGROUND

The vestibular schwannoma (VS) secretome can initiate monocyte recruitment and macrophage polarization to M1 (proinflammatory) and/or M2 (protumorigenic) phenotypes, which in turn secrete additional cytokines that contribute to the tumor microenvironment. Profiling cyst fluid and cerebrospinal fluid (CSF) in cystic VS provides a unique opportunity to understand mechanisms that may contribute to tumor progression and cyst formation.

HYPOTHESIS

Cystic VSs secrete high levels of cytokines into cyst fluid and express abundant M1 and M2 macrophages.

METHODS

Tumor, CSF, and cyst fluid were prospectively collected from 10 cystic VS patients. Eighty cytokines were measured in fluid samples using cytokine arrays and compared with normal CSF from normal donors. Immunofluorescence was performed for CD80 + M1 and CD163 + M2 macrophage markers. Demographic, audiometric, and radiographic information was obtained through retrospective chart review.

RESULTS

Cyst fluid expressed more osteopontin and monocyte chemotactic protein-1 (MCP-1; p < 0.0001), when compared with normal CSF. Cyst fluid also expressed more protein ( p = 0.0020), particularly MCP-1 ( p < 0.0001), than paired CSF from the same subjects. MCP-1 expression in cyst fluid correlated with CD80 + staining in VS tissue ( r = 0.8852; p = 0.0015) but not CD163 + staining.

CONCLUSION

Cyst fluid from cystic VS harbored high levels of osteopontin and MCP-1, which are cytokines important in monocyte recruitment and macrophage polarization. MCP-1 may have a significant role in molding the tumor microenvironment, by polarizing monocytes to CD80 + M1 macrophages in cystic VS. Further investigations into the role of cytokines and macrophages in VS may lead to new avenues for therapeutic intervention.

Predictive Value of K i -67 Index in Evaluating Sporadic Vestibular Schwannoma Recurrence: Systematic Review and Meta-analysis

Introduction  K _i -67 is often used as a proliferation index to evaluate how aggressive a tumor is and its likelihood of recurrence. Vestibular schwannomas (VS) are a unique benign pathology that lends itself well to evaluation with K _i -67 as a potential marker for disease recurrence or progression following surgical resection. Methods  All English language studies of VSs and K _i -67 indices were screened. Studies were considered eligible for inclusion if they reported series of VSs undergoing primary resection without prior irradiation, with outcomes including both recurrence/progression and K _i -67 for individual patients. For published studies reporting pooled K _i -67 index data without detailed by-patient values, we contacted the authors to request data sharing for the current meta-analysis. Studies reporting a relationship between K _i -67 index and clinical outcomes in VS for which detailed patients' outcomes or K _i -67 indices could not be obtained were incorporated into the descriptive analysis, but excluded from the formal (i.e., quantitative) meta-analysis. Results  A systematic review identified 104 candidate citations of which 12 met inclusion criteria. Six of these studies had accessible patient-specific data. Individual patient data were collected from these studies for calculation of discrete study effect sizes, pooling via random-effects modeling with restricted maximum likelihood, and meta-analysis. The standardized mean difference in K _i -67 indices between those with and without recurrence was calculated as 0.79% (95% confidence interval [CI]: 0.28-1.30; p  = 0.0026). Conclusion  K _i -67 index may be higher in VSs that demonstrate recurrence/progression following surgical resection. This may represent a promising means of evaluating tumor recurrence and potential need for early adjuvant therapy for VSs.

Increased Circulating Chemokines and Macrophage Recruitment in Growing Vestibular Schwannomas

BACKGROUND

There is evidence that macrophage infiltration in the tumor microenvironment promotes vestibular schwannoma (VS) growth. Efficacy of bevacizumab in NF2-associated VS demonstrates the value of therapies targeting the microvascular tumor microenvironment, and tumor-associated macrophages (TAMs) may represent another druggable target.

OBJECTIVE

To characterize the relationship between growth, TAM infiltration, and circulating monocyte chemokines in a large cohort of patients with VS.

METHODS

Immunostaining for Iba1 (macrophages), CD31 (endothelium), and fibrinogen (permeability) was performed on 101 growing and 19 static sporadic VS. The concentrations of monocyte-specific chemokines were measured in the plasma of 50 patients with growing VS and 25 patients with static VS.

RESULTS

The Iba1 + cell count was significantly higher in growing as compared with static VS (592 vs 226/×20 HPF, P =<0.001). Similarly, the CD31 + % surface area was higher in growing VS (2.19% vs 1.32%, P = .01). There was a positive correlation between TAM infiltration and VS growth rate, which persisted after controlling for the effect of tumor volume (aR2 = 0.263, P =<0.001). The plasma concentrations of several monocytic chemokines were higher in patients with growing rather than static VS.

CONCLUSION

There is a strong positive correlation between TAM infiltration and volumetric growth of VS, and this relationship is independent of tumor size. There is a colinear relationship between TAM infiltration and tumor vascularity, implying that inflammation and angiogenesis are interlinked in VS. Chemokines known to induce monocyte chemotaxis are found in higher concentrations in patients with growing VS, suggestive of a potential pathophysiological mechanism.

How to position the patient? A meta-analysis of positioning in vestibular schwannoma surgery via the retrosigmoid approach

Objective

Patient positioning is a matter of ongoing debate in the surgical treatment of vestibular schwannoma (VS). Main endpoints of this discussion are preservation of facial nerve functioning, extent of resection, and complications. In this meta-analysis, we aim to investigate the impact of patient positioning on VS surgery via the retrosigmoid approach.

Methods

We searched for eligible comparative trials on PubMed, Cochrane library, and Web of Science. Positioning groups were compared regarding facial nerve outcome, extent of resection, postoperative hydrocephalus, postoperative CSF leaks, perioperative venous air embolism, and perioperative mortality. Two groups of positions were defined, and the following positions were allocated to those groups: (1) Semi-sitting and Sitting-position; (2) Lateral position, supine position with extensive head rotation, lateral oblique (=Fukushima/Three-quarter prone), and park-bench position.

Results

From 374 full-text screenings, 7 studies met the criteria and were included in our meta-analysis comprising 1640 patients. Our results demonstrate a significantly better long-term (≥6 months) outcome of the facial nerve after VS surgery in the semi-sitting positioning (OR: 1.49, 95%CI: 1.03-2.15, p = 0.03). Positioning did not influence the extent of resection, rate of postoperative CSF leaks, and the presence of a postoperative hydrocephalus. Overall incidence of venous air embolisms was significantly associated with VS surgery in sitting positioning (OR: 6.77, 95% CI: 3.66-12.54, p < 0.00001). Perioperative mortality was equal among both positioning groups.

Conclusion

Semi-sitting positioning seems to be associated with an improved facial nerve outcome after VS surgery via the retrosigmoid approach. Venous air embolisms are significantly more often observed among VS patients who underwent surgery in the sitting position, but the perioperative mortality is equal in both positioning groups. Both positioning groups are a safe procedure. Multicentric prospective randomized trials are needed to evaluate the risk-benefit ratio of each positioning in VS surgery via the retrosigmoid approach.

Tumor Biology and Microenvironment of Vestibular Schwannoma-Relation to Tumor Growth and Hearing Loss

Vestibular schwannoma is the most common benign neoplasm of the cerebellopontine angle. It arises from Schwann cells of the vestibular nerve. The first symptoms of vestibular schwannoma include hearing loss, tinnitus, and vestibular symptoms. In the event of further growth, cerebellar and brainstem symptoms, along with palsy of the adjacent cranial nerves, may be present. Although hearing impairment is present in 95% of patients diagnosed with vestibular schwannoma, most tumors do not progress in size or have low growth rates. However, the clinical picture has unpredictable dynamics, and there are currently no reliable predictors of the tumor's behavior. The etiology of the hearing loss in patients with vestibular schwannoma is unclear. Given the presence of hearing loss in patients with non-growing tumors, a purely mechanistic approach is insufficient. A possible explanation for this may be that the function of the auditory system may be affected by the paracrine activity of the tumor. Moreover, initiation of the development and growth progression of vestibular schwannomas is not yet clearly understood. Biallelic loss of the NF2 gene does not explain the occurrence in all patients; therefore, detection of gene expression abnormalities in cases of progressive growth is required. As in other areas of cancer research, the tumor microenvironment is coming to the forefront, also in vestibular schwannomas. In the paradigm of the tumor microenvironment, the stroma of the tumor actively influences the tumor's behavior. However, research in the area of vestibular schwannomas is at an early stage. Thus, knowledge of the molecular mechanisms of tumorigenesis and interactions between cells present within the tumor is crucial for the diagnosis, prediction of tumor behavior, and targeted therapeutic interventions. In this review, we provide an overview of the current knowledge in the field of molecular biology and tumor microenvironment of vestibular schwannomas, as well as their relationship to tumor growth and hearing loss.

Predictors of Recurrence After Sub-total or Near-total Resection of Vestibular Schwannoma: Importance of Tumor Volume and Ventral Extension

OBJECTIVE

To evaluate the predictors of remnant tumor regrowth and need for salvage therapy after less than gross total resection (GTR) of vestibular schwannoma (VS).

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary neurotologic referral center.

PATIENTS

Patients who underwent VS resection between 2008 and 2019 either with GTR, near total resection (NTR), and subtotal resection (STR).

INTERVENTIONS

Microsurgical resection, salvage radiosurgery.

MAIN OUTCOME MEASURES

Regrowth free interval, salvage free interval, tumor doubling rate.

RESULTS

Three hundred eighty five cases (GTR = 236, NTR = 77, and STR = 71) from 2008 to 2019 were included. STR cohort had much larger and complex tumors with significant differences in tumor volume, ventral extension and brainstem compression (p  < 0.001). On single predictor analysis, tumor volume, ventral extension, brainstem compression as well as STR strategy was associated with significant increased risk of regrowth and need for salvage therapy. Multivariate analysis revealed STR strategy as significant predictor of regrowth (hazard ratio 3.79, p  < 0.0005). Absolute remnant volume and extent of resection (EOR) did not predict regrowth. A small proportion of cases (NTR = 4%, STR = 15%) eventually needed salvage radiosurgery with excellent ultimate local tumor control with no known recurrence to date.

CONCLUSIONS

Conservative surgical strategy employing NTR or STR can be employed safely in large and complex VS. While there is increased risk of regrowth in the STR cohort, excellent local control can be achieved with appropriate use of salvage radiosurgery. No disceret radiologic or operative predictors of regrowth were identified.

A Nomogram to Predict Recurrence-Free Survival Following Surgery for Vestibular Schwannoma

Background

Vestibular schwannoma (VS) is the most common benign tumor of the posterior fossa. The recurrence of VS has always received widespread attention. This study aimed to develop a nomogram to predict Recurrence-free survival (RFS) following resection of VS.

Methods

A total of 425 patients with VS who underwent resection at the Department of Neurosurgery in Chinese PLA General Hospital between January 2014 and December 2020 were enrolled in this retrospective study. The medical records and follow-up data were collected. Cox regression analysis was used to screen prognostic factors and construct the nomogram. The predictive accuracy and clinical benefits of the nomogram were validated using the area under the curve (AUC), calibration curves, and decision curve analysis (DCA).

Results

The Cox regression analysis revealed that age (HR = 0.96; 95% CI 0.94 - 0.99; p < 0.01), EOR (HR = 4.65; 95% CI 2.22 - 9.74; p < 0.001), and Ki-67 (HR = 1.16; 95% CI 1.09 - 1.23; p < 0.001) were all significantly correlated with recurrence, and they were finally included in the nomogram model. The concordance index of the nomogram was 0.86. The areas under the curve (AUCs) of the nomogram model of 3-, 4- and 5-year were 0.912, 0.865, and 0.809, respectively. A well-fitted calibration curve was also generated for the nomogram model. The DCA curves also indicated that the nomogram model had satisfactory clinical utility compared to the single indicators.

Conclusions

We developed a nomogram that has high accuracy in predicting RFS in patients after resection of VS. All of the included prognostic factors are easy to obtain. The nomogram can improve the postoperative management of patients and assist clinicians in individualized clinical treatment. Furthermore, we generated a web-based calculator to facilitate clinical application: https://abc123-123.shinyapps.io/VS-RFS/.

Tumor-Associated Macrophages in Vestibular Schwannoma and Relationship to Hearing

Objective

(1) Characterize the distribution of M1 and M2 macrophages in vestibular schwannomas by hearing status. (2) Develop assays to assess monocyte migration and macrophage polarization in cocultures with vestibular schwannoma cells.

Study Design

Basic and translational science.

Setting

Tertiary care center.

Methods

A retrospective chart review of 30 patients with vestibular schwannoma (VS) was performed. Patients were stratified into serviceable and unserviceable hearing groups. Immunohistochemistry for CD80⁺ M1 and CD163⁺ M2 macrophages was conducted. Primary VS cultures (n = 4) were developed and cocultured with monocytes. Immunohistochemistry for macrophage markers was performed to assess monocyte migration and macrophage polarization.

Results

Although tumors associated with unserviceable hearing had higher levels of CD80 and CD163 than those with serviceable hearing, the relationship was only significant with CD163 (P = .0161). However, CD163 level did not remain a significant predictor variable associated with unserviceable hearing on multivariate analysis when adjusted for other variables. In vitro assays show that VS cells induced monocyte migration and polarization toward CD80⁺ M1 or CD163⁺ M2 macrophage phenotypes, with qualitative differences in CD163⁺ macrophage morphologies between serviceable and unserviceable hearing groups.

Conclusion

Vestibular schwannomas express varying degrees of CD80⁺ M1 and CD163⁺ M2 macrophages. We present evidence that higher expression of CD163⁺ may contribute to poorer hearing outcomes in patients with VS. We also describe in vitro assays in a proof-of-concept investigation that VS cells can initiate monocyte migration and macrophage polarization. Future investigations are warranted to explore the relationships between tumor, macrophages, secreted cytokines, and hearing outcomes in patients with VS.

Dramatic Growth of a Vestibular Schwannoma After 16 Years of Postradiosurgery Stability in Association With Exposure to Tyrosine Kinase Inhibitors

BACKGROUND

Vestibular schwannoma (VS) is a benign nerve-sheath tumor that sporadically displays aggressive behavior - often attributable to intrinsic tumor biology and an unfavorable immune microenvironment. However, the potential for idiosyncratic responses on VS growth to novel biologics is largely unknown.

METHODS

Case report.

RESULTS

A 57-year-old man underwent stereotactic radiosurgery (SRS) for a small intracanalicular presumed VS, which presented with left-sided hearing loss and episodic vertigo. Treatment response was excellent, with >50% reduction in tumor volume and confirmed stability at 14 years post-SRS radiographic follow-up. The patient subsequently developed an unrelated metastatic gastrointestinal tumor, and was started on tyrosine kinase inhibitors. Within 12-months of regorafenib treatment, and 16-years since SRS, the patient developed ipsilateral House-Brackmann Grade IV facial weakness. Dramatic VS expansion from 14 to 25 mm in maximum diameter, with new brain stem compression, was seen on MRI. Due to poor prognosis of his gastrointestinal malignancy, he declined surgical resection, and elected for palliative salvage SRS.

CONCLUSION

We report the case of VS with radiographically proven stability for >14 years that underwent dramatic tumor progression after treatment with tyrosine kinase inhibitors. The dynamics between systemic immunomodulation and VS disease phenotype remain incompletely understood, and there may be potential for unintended iatrogenic VS progression.

Neuro-Ophthalmic Complications of Vestibular Schwannoma Resection: Current Perspectives

Vestibular schwannomas (VSs), also called acoustic neuromas, are benign intracranial neoplasms of the vestibulocochlear (VIII) cranial nerve. Management options include “wait-and-scan,” stereotactic radiosurgery and surgical resection. Due to the proximity of the VIII nerve to the facial (VII) nerve in the cerebello-pontine angle, the VII nerve is particularly vulnerable to the effects of surgical resection. This can result in poor eye closure, lagophthalmos and resultant corneal exposure post VS resection. Additionally, compression from the tumor or resection can cause trigeminal (V) nerve damage and a desensate cornea. The combination of an exposed and desensate cornea puts the eye at risk of serious ocular complications including persistent epithelial defects, corneal ulceration, corneal vascularization, corneal melting and potential perforation. The abducens (VI) nerve can be affected by a large intracranial VS causing raised intracranial pressure (a false localizing sign) or as a result of damage to the VI nerve at the time of resection. Other types of neurogenic strabismus are rare and typically transient. Contralaterally beating nystagmus as a consequence of vestibular dysfunction is common post-operatively. This generally settles to pre-operative levels as central compensation occurs. Ipsilaterally beating nystagmus post-operatively should prompt investigation for post-operative cerebrovascular complications. Papilledema (and subsequent optic atrophy) can occur as a result of a large VS causing raised intracranial pressure. Where papilledema follows surgical resection of a VS, it can indicate that cerebral venous sinus thrombosis has occurred. Poor visual function following VS resection can result as a combination of all these potential complications and is more likely with larger tumors.

Growth arrest of a refractory vestibular schwannoma after anti-PD-1 antibody treatment

A 25-year-old man presented with left-sided hearing loss, blurred vision and papilloedema. Imaging revealed a large, left-sided, contrast-enhancing cerebellopontine mass causing obstructive hydrocephalus, consistent with vestibular schwannoma (VS). Following an incomplete resection via retrosigmoid craniotomy at an outside facility, he was referred to our department, and cerebrospinal fluid diversion followed by repeat resection was recommended. A subtotal resection was achieved, and the patient was subsequently treated with adjuvant stereotactic radiosurgery (SRS). Progressive interval growth was observed on serial post-SRS MRI studies; correspondingly, at 31 months after treatment, the patient was initiated on antiprogrammed-death receptor 1 (PD-1) antibody treatment with pembrolizumab. Growth arrest was noted on subsequent serial imaging studies, which have been maintained for a total of 30 months since initiation of a 18-month anti-PD-1 course of therapy. Additional case accumulation and translational study is required to better characterise this therapeutic strategy; however, PD-1/programmed death-ligand 1 inhibition may offer a promising salvage therapy for refractory VS.

Inner Ear Enhancement With Delayed 3D-FLAIR MRI Imaging in Vestibular Schwannoma

OBJECTIVES

To evaluate blood-labyrinth barrier permeability using delayed gadolinium enhanced three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) in patients with untreated sporadic vestibular schwannoma (VS) to interrogate the etiopathogenesis of progressive sensorineural hearing loss.

DESIGN

Prospective case series.

SETTING

Single institution tertiary care center.

PARTICIPANTS

Patients with previously untreated small to medium-sized unilateral VS undergoing 3D-FLAIR imaging 10 minutes (immediate) and 5 to 8 hours (delayed) after administration of intravenous gadolinium.

MAIN OUTCOME MEASURES

Comparison of cochlear and vestibular signal intensity ratios (SIRs) across immediate and delayed images and across the tumor and nontumor ear.

RESULTS

Six of eight (75%) patients demonstrated asymmetric enhancement of inner ear structures on delayed contrast-enhanced imaging. Delayed mean cochlea and vestibule SIRs were significantly greater than immediate SIRs (cochlea: 1.91 versus 1.21 [p = 0.02]; vestibule 1.74 versus 1.15 [p = 0.02]). A higher vestibule SIR was statistically significantly associated with poorer pure-tone average and word recognition scores (p = 0.001).

CONCLUSION

Ears with VS exhibited increased enhancement on delayed 3D FLAIR imaging. These findings suggest that alterations in blood-labyrinth barrier permeability may explain progressive sensorineural hearing loss in a subset of patients with untreated VS.

Predominance of M1 subtype among tumor-associated macrophages in phenotypically aggressive sporadic vestibular schwannoma

OBJECTIVE

Tumor-associated macrophages (TAMs) have been implicated as pathologic actors in phenotypically aggressive vestibular schwannoma (VS), potentially mediated via programmed death-ligand 1 (PD-L1). The authors hypothesized that PD-L1 is a key regulator of the VS immune microenvironment.

METHODS

Forty-six consecutive, radiation-naïve, sporadic VSs that were subtotally resected at primary surgery were assessed via immunohistochemical analysis, including analysis of CD163 and PD-L1 expression. Pathologic data were correlated with clinical endpoints, including tumor control, facial nerve function, and complications.

RESULTS

Baseline parameters were equivalent between stable and progressive post-subtotal resection (STR) VS. CD163 percent positivity and M2 index were significantly increased among tumors that remained stable (34% vs 21%, p = 0.02; 1.13 vs 0.99, p = 0.0008), as well as patients with favorable House-Brackmann grade I or II facial nerve function (31% vs 13%, p = 0.04; 1.11 vs 0.97, p = 0.05). PD-L1 percent positivity was significantly associated with tumor progression (1% vs 11%, p = 0.01) and unfavorable House-Brackmann grade III-VI facial nerve function (1% vs 38%, p = 0.02). On multivariate analysis, PD-L1 was independently significant in all models (likelihood ratio 4.4, p = 0.04), while CD163 was dependent in all iterations.

CONCLUSIONS

In contrast to prior reports, in this study, the authors observed significantly increased levels of M1, CD163+ TAMs in association with VS that progressed after STR. Progressive tumors are characterized by increased PD-L1, potentially highlighting a mechanism of immune evasion that results in TAM deactivation, tumor growth, and further infiltration of anti-tumor immune cells. Targeting PD-1/PD-L1 may offer therapeutic promise, particularly in the setting of disease control after STR.