Subtotal resection of vestibular schwannoma: Evaluation with Ki-67 measurement, magnetic resonance imaging, and long-term observation

Outcomes of Near-Total and Subtotal Resection of Sporadic Vestibular Schwannoma: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate tumor control and facial nerve outcomes after gross-total (GTR), near-total (NTR), and subtotal resection (STR) of sporadic vestibular schwannomas (VS).

DATA SOURCES

PubMed, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus databases were searched in August 2021 through inception following PRISMA guidelines.

REVIEW METHODS

English language articles reporting tumor control and facial nerve outcomes of adults (≥18 years) with NTR and STR of VS were evaluated. Study characteristics, demographics data, tumor characteristics, type of surgical intervention, and outcome measures on tumor control and facial nerve function were collected. Pooled relative risk (RR) estimates for tumor recurrence and facial nerve outcomes were calculated and stratified by extent of resection.

RESULTS

From an initial search of 2504 articles, 48 studies were included in the analysis. When comparing 1108 patients who underwent NTR to 3349 patients with GTR, the pooled RR of recurrence in the NTR cohort was 2.94 (95% confidence interval [CI] 1.65-5.24, P = .0002). When comparing 1016 patients who underwent STR to 6171 patients with GTR, the pooled RR of recurrence in the STR cohort was 11.50 (95% CI 6.64-19.92, P < .0001). Estimates for risk of tumor regrowth for less-than-complete resection are presented. There was no elevated risk of adverse facial nerve outcome (defined as House-Brackmann grade III and above) in each category of extent of resection compared to GTR.

CONCLUSION

Extent of resection predicts risk of tumor recurrence/regrowth following microsurgical resection. Favorable facial nerve outcome should be weighed against the increased risk of regrowth and the potential need for further treatment.

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.

Postoperative Intratumoral or Peritumoral Hematomas After Vestibular Schwannoma Resection

BACKGROUND

Surgical removal of a vestibular schwannoma is a complex and challenging procedure, which may be complicated by development of postoperative hematomas, particularly after incomplete resection of the tumor.

OBJECTIVE

To investigate the occurrence of postoperative intra- or peritumoral hematomas after surgery for a vestibular schwannoma.

METHODS

This retrospective study evaluated 49 patients (age range 17-78 years) with a vestibular schwannoma, who were treated surgically via the lateral suboccipital approach between 2011 and 2016. The tumors ranged in size from 0 mm (in a case of an intracanalicular lesion) to 56 mm. In 30 cases (61%), total or near-total resection was accomplished, and in 19 cases (39%), subtotal or partial resection was done. On the basis of their bleeding tendency during tumor removal, the patients were divided into a "less-bleeding" (38 cases; 78%) and a "more-bleeding" (11 cases; 22%) subgroups.

RESULTS

A maximal vestibular schwannoma diameter >30 mm, patient age >60 years, and more bleeding during tumor removal were significantly associated with incomplete (subtotal or partial) resection. In six cases (12%), serial computed tomography after surgery demonstrated a postoperative hematoma, which was caused by insufficient irrigation of the surgical field (in two cases) or resulted from peritumoral hemorrhage (in two cases), intratumoral hemorrhage (in one case), or both intra- and peritumoral hemorrhage (in one case). The latter patient required urgent reoperation. In all cases, postoperative hematomas occurred after incomplete (subtotal or partial) resection of a vestibular schwannoma, and their development was significantly associated with more bleeding during tumor removal.

CONCLUSION

For avoidance of postoperative hematomas, careful hemostasis is required after completion of vestibular schwannoma removal, especially in cases with incomplete resection and an excessive bleeding tendency of the tumor tissue.

Evaluating growth trends of residual sporadic vestibular schwannomas: a systematic review and meta-analysis

BACKGROUND

Gross total resection remains the gold-standard approach for vestibular schwannomas (VS) when surgery is indicated. In select cases, incomplete resection (IR) becomes a desired alternative to preserve the facial nerve function and the patient's quality of life. While a lot of earlier studies described incompletely resected sporadic VSs as dormant, more recent studies reported a higher growth rate following IR, therefore an evaluation of the residual VS growth rates could have important implications for the follow-up treatment protocols and provide relevant information for neurosurgeons, neuro-otologists, neuropathologists, and radiologists. Although prognostic factors predicting preoperative VS growth have been previously investigated, these factors have not been investigated following IR. Our review aims to examine the growth rate of residual sporadic VS following IR and to examine variables associated with the regrowth of residual VS.

METHODS

The review was conducted in accordance with the PRISMA guidelines. Six databases (MEDLINE (Ovid), Embase (Ovid), CINAHL Plus (EBSCO), Cochrane Central Register of Controlled Trials (CENTRAL), WHO International Clinical Trials Registry Platform and UK Clinical Trials Gateway (WHO ICTRP) were searched. Full-text articles analysing growth rates in at least ten patients who had residual VS after IR were assessed. We conducted a meta-analysis using a random-effects model via RevMan.

RESULTS

14 studies totalling 849 patients were included in the analysis. The mean planimetric growth rate was 1.57 mm/year (range 0.16-3.81 mm/year). The mean volumetric growth rate was 281.725 mm³/year (range 17.9-530.0 mm³/year). Age, sex, pre-operative tumour size/volume, cystic tumour sub-type, MIB-1 index, and intracanalicular tumour location were not associated with residual growth. Residual tumour size/volume was statistically significant to growth (OR = 0.65, 95% CI 0.47-0.90, p = 0.01). Radiological re-growth occurred in an average of 26.6% of cases (range 0-54.5%).

CONCLUSION

From our analysis, only the residual tumour volume/size was associated with residual VS growth. Therefore, close postoperative surveillance for the first year, followed by an annual MRI scan for at least 5 years, and subsequently extended interval surveillance remains of utmost importance to monitor disease progression and provide timely surgical and adjuvant interventions. Our study shows that future work should be aimed at molecular and histological characteristics of residual VSs to aid prognostic understanding of growth.

Facial Nerve Function Outcome and Risk Factors in Resection of Large Cystic Vestibular Schwannomas

Objective Cystic vestibular schwannomas (VS) in contrast to solid VS tend to have accelerated growth, larger volume, rapid/atypical presentation, lobulated/adherent surface, and unpredictable course of the cranial nerves. Cystic VS are surgically challenging, with worse clinical outcomes and higher rate of subtotal resection (STR).

Methods We retrospectively analyzed postoperative outcomes of 125 patients with cystic VS, operated between years 2005 and 2019 in our center. We confronted the extent of the resection and House-Brackmann (HB) grade of facial palsy with the results of comparable cohort of patients with solid VS operated in our center and literature review by Thakur et al.1

Results Translabyrinthine approach was preferred for resection of large, cystic VS (97.6%). Gross-total resection (GTR) was achieved in 78 patients (62.4%), near-total resection (NTR) with remnant (<4 × 4 × 2 mm) in 43 patients (34.4%), and STR in 4 patients (3.2%). NTR/STR were significantly associated with higher age, tumor volume >5 cm3, retrosigmoid approach, high-riding jugular bulb, tumor adherence to the brain stem, and facial nerve (p = 0.016; 0.003; 0.005; 0.025; 0.001; and <0.00001, respectively).

One year after the surgery, 76% of patients had HB grades 1 to 2, 16% had HB grades 3 to 4, and 8% had HB grades 5 to 6 palsy. Worse outcome (HB grades 3 to 6) was associated with preoperative facial palsy, tumor volume >25 cm3, and cyst over the brain stem (p = 0.045; 0.014; and 0.05, respectively). Comparable solid VS operated in our center had significantly higher HB grades 1 to 2 rate than our cystic VS (94% versus 76%; p = 0.03). Comparing our results with literature review, our HB grades 1 to 2 rate was significantly higher (76% versus 39%; p = 0.0001). Tumor control rate 5 years after surgery was 95.8%.

Conclusion Our study confirmed that microsurgery of cystic VS has worse outcomes of facial nerve preservation and extent of resection compared with solid VS. Greater attention should be paid to the above-mentioned risk factors.

The behavior of residual tumors following incomplete surgical resection for vestibular schwannomas

The management of vestibular schwannoma (VS) with residual tumor following incomplete resection remains controversial and little is known regarding postoperative tumor volume changes. The behavior of residual tumors was analyzed for 111 patients who underwent surgery for newly diagnosed VS between September 2006 and July 2017. The postoperative tumor volume changes were assessed during a mean follow-up of 69 months (range 36–147 months). Fifty-three patients underwent imaging surveillance following incomplete resection. There was no residual tumor growth in 44 patients (83%). A significant regression of residual tumor volume was noted in the no growth group at postoperative 1 year (p = 0.028), 2 years (p = 0.012), but not from 3 years onwards. Significant predictors of regrowth were immediate postoperative tumor volume ≥ 0.7 cm³ (HR 10.5, p = 0.020) and residual tumor location other than the internal auditory canal (IAC) (HR 6.2, p = 0.026). The mean time to regrowth was 33 months (range 5–127 months). The 2-, 5-, and 10-year regrowth-free survival rates were 90.6%, 86.8%, and 83%, respectively. In conclusion, significant residual tumor regression could occur within 2 years for a VS with an immediate postoperative tumor volume less than 0.7 cm³ or residual tumor in IAC.

[Vestibular schwannoma: Diagnosis-Therapy-Aftercare]

Vestibularisschwannome können die Lebensqualität von Patienten stark beeinträchtigen. Neben einer eingeschränkten Hörfunktion wird die Gesichtslähmung hierbei als besonders störend empfunden. Unterschiedliche Wachstumsraten dieser gutartigen Tumore erschweren die zeitliche Vorhersage einer funktionellen Beeinträchtigung von Hirnnerven. Deshalb ist ein regelmäßiges Update zu aktuellen Therapiestrategien und alternative Behandlungsmöglichkeiten sowohl für Ärzte als auch Patienten relevant.

Facial nerve outcomes following gamma knife radiosurgery for subtotally resected vestibular schwannomas: Early versus delayed timing of therapy

OBJECTIVES

Initially treating vestibular schwannomas (VSs) with subtotal resection (STR) followed by Gamma Knife radiosurgery (GKRS) for progression of tumor residual is a strategy that balances maximal tumor resection with preservation of neurological function. The effect of timing of GKRS for residual and recurrent VSs remains poorly defined. We developed a simple and practical treatment algorithm for the timing of GKRS after STR of VSs and reviewed our follow-up results to determine outcomes between patients treated with early vs. late GKRS.

PATIENTS AND METHODS

Patients that underwent STR between 1999 and 2017 for a VS at Tufts Medical Center were identified and included in the study cohort. Patients who received GKRS ≤ 12 months after STR were included in the early intervention group. Patients who received GKRS > 12 months after STR or did not have tumor progression on follow-up thus not requiring GKRS were included in the observation/delayed intervention group.

RESULTS

STR of VSs was performed on 23 patients. Mean patient age at the time of STR was 53.0 years (range: 20-86.2). The mean follow-up was 4.2 years (range: 1 month-15.5 years). Patients most frequently presented with hearing loss. There were 5 patients (21.7 %) in the early intervention group and 18 (78.3 %) patients in the observation/delayed intervention group. Ten of 23 patients (43.5 %) required GKRS. Thirteen (56.5 %) did not receive GKRS. None of the patients in the early intervention group or the observation/delayed intervention group had changes in House-Brackmann (HB) Grade either after GKRS or at the end of the study period.

CONCLUSIONS

GKRS of residual or recurrent tumor is safe following STR of VS and appears to carry a low risk of worsening facial nerve function when performed for progressive tumor growth.

The impact of the MIB-1 index on facial nerve outcomes in vestibular schwannoma surgery

Background

Facial nerve palsy is a severe morbid condition that occurs after vestibular schwannoma (VS) surgery. The objective of this study was to evaluate facial nerve outcomes based on surgical techniques, tumour size, and immunohistochemical factors.

Methods

One hundred eighteen patients with VS were retrospectively analysed. Gross total resection (GTR) was achieved in 83 patients, and subtotal resection (STR) was achieved in 35 patients. Follow-up was 60 months (median). Facial nerve outcomes were assessed for 24 months after surgery. Analysis of the MIB-1 index was performed in 114 patients (97%) to evaluate recurrence and facial nerve outcomes.

Results

Immediately after surgery, 16 of 35 patients (45.7%) with STR and 21 of 83 patients (25.3%) with GTR had a good (House-Brackmann (HB) score ≤ 2) facial nerve outcome (p = 0.029). Semi-sitting positioning (p = 0.002) and tumour size class of 3 (> 4 cm) were also associated with worse HB outcomes after 2 years (p = 0.004) in univariate analyses. The MIB-1 index was significantly correlated with diffuse infiltration of tumour-associated CD45⁺ lymphocytes (r = 0.63, p = 0.015) and CD68⁺ macrophages (r = 0.43, p = 0.021). ROC analysis found an AUC of 0.73 (95% CI = 0.60–0.86, p = 0.003) for the MIB-1 index in predicting poor facial nerve outcomes. Binary logistic regression analysis revealed an MIB-1 index ≥ 5% (16/28 (57.1%) vs. 5/40 (12.5%); p < 0.001, OR = 14.0, 95% CI = 3.2–61.1) and a tumour size class of 3 (6/8 (75.0%) vs. 2/8 (25.0%); p = 0.01, OR = 14.56, 95% CI = 1.9–113.4) were predictors of poor HB scores (≥ 3) after 1 year.

Conclusions

An MIB-1 index ≥ 5% seems to predict worse long-term facial nerve outcomes in VS surgery.

Management of NF2-associated vestibular schwannomas in children and young adults: influence of surgery and clinical factors on tumor volume and growth rate

OBJECTIVE

The authors' aim was to evaluate the tumor volume and growth rate of neurofibromatosis type 2 (NF2)-associated vestibular schwannomas (VSs) and the clinical factors or type of mutations before and after surgery in children and adults younger than 25 years at the time of diagnosis.

METHODS

A total of 579 volumetric measurements were performed in 46 operated tumors in 28 NF2 patients, using thin-slice (< 3 mm) T1-weighted contrast-enhanced MRI. The follow-up period ranged from 21 to 167 months (mean 75 months). Growth rate was calculated using a multilinear regression model. Mutation analysis of the NF2 gene was performed in 25 patients.

RESULTS

Surgery significantly (p = 0.013) slowed the VS growth rate from 0.69 ± 1.30 cm3/yr to 0.23 ± 0.42 cm3/yr. Factors significantly associated with a higher growth rate of VSs were increasing patient age (p < 0.0005), tumor volume (p = 0.006), tumor size (p = 0.001), and constitutional truncating mutations in the NF2 gene (p = 0.018). VS growth rates tended to be higher in patients with spinal ependymomas and in right-sided tumors and lower in the presence of peripheral schwannomas; however, no statistical significance was achieved.

CONCLUSIONS

Decompression of the internal auditory canal with various degrees of tumor resection decreases the postoperative tumor growth rate in children and young adults with NF2-associated VS. Patients with potential risk factors for accelerated growth (e.g., large volume, truncating mutations) and with increasing age should be monitored more closely before and after surgery.

COX2 expression is associated with proliferation and tumor extension in vestibular schwannoma but is not influenced by acetylsalicylic acid intake

Acetylsalicylic acid has been linked to a lower risk for different cancer types, presumably through its inhibitory effect on cyclooxygenase 2. This has also been investigated in vestibular schwannomas with promising results suggesting an antiproliferative effect and recently the intake has been recommended for vestibular schwannomas as a conservative treatment option. We constructed tissue microarrays from paraffin-embedded tissue samples of 1048 vestibular schwannomas and analyzed the expression of cyclooxygenase 2 and the proliferation marker MIB1 (Molecular Immunology Borstel) via immunohistochemistry together with clinical data (age, gender, tumor extension, prior radiotherapy, neurofibromatosis type 2, tumor recurrence, cyclooxygenase 2 responsive medication). Univariate analysis showed that cyclooxygenase 2 expression was increased with age, female gender, prior radiotherapy and larger tumor extension. MIB1 expression was also associated with higher cyclooxygenase 2 expression. Schwannomas of neurofibromatosis type 2 patients had lower cyclooxygenase 2 levels. Use of acetylsalicylic acid, non-steroidal anti-inflammatory drugs, glucocorticoids or other immunosuppressants did not show differences in cyclooxygenase 2 or MIB1 expression. Instead, cyclooxygenase 2 expression increases with tumor extension while MIB1 expression is not associated with tumor size. Overall, cyclooxygenase 2 expression is associated with proliferation but not influenced by regular intake of acetylsalicylic acid or other cyclooxygenase 2-responsive medications. Acetylsalicylic acid intake does not alter cyclooxygenase 2 expression and has no antiproliferative effect in vestibular.

Hyperbaric oxygen as an adjuvant to temozolomide nanoparticle inhibits glioma growth by inducing G2/M phase arrest

AIM

To study the effects of combinational treatment of hyperbaric oxygen (HBO) and nanotemozolomide in glioma.

MATERIALS & METHODS

Temozolomide (TMZ)-loaded porous silicon nanoparticles (TMZ/PSi NPs) were prepared. In vitro and in vivo evaluations were performed.

RESULTS

The cell uptake of TMZ/PSi NPs could be tracked by autofluorescence of porous silicon. The concentration of oxygen in tumor was improved and the antitumor rate was increased to 84.2% in the TMZ/PSi NPs combined with HBO group. The viability of hypoxia-induced glioma C6 cells was decreased and cell cycle was arrested at G2/M phase in response to TMZ/PSi NPs treatment with HBO compared with continuous treatment with hypoxia.

CONCLUSION

The combinational treatment of TMZ/PSi NPs and HBO could be a promising therapeutic strategy for glioma.