Surgical management of vestibular schwannomas after failed radiation treatment

"Salvage surgery for vestibular schwannomas after failed stereotactic radiosurgery or radiation: A systematic review and meta-analysis"

INTRODUCTION

Stereotactic radiosurgery effectively controls vestibular schwannoma (VS). However, in certain cases, microsurgical resection may be necessary for tumor progression after radiosurgery or, after failure of the latter. The results on the safety and efficacy of salvage surgery for VS are still unclear, with scarce literature on the subject.

OBJECTIVE

The present study aimed to evaluate the safety and efficacy of salvage surgery on the resection of vestibular schwannomas that have been previously treated with stereotactic radiosurgery or radiotherapy.

METHODS

Following PRISMA guidelines, we searched Medline, Embase, and Web of Science databases. We used single proportion analysis with 95 % confidence intervals under a random-effects model, I2 to assess heterogeneity, and Baujat and sensitivity analysis to address high heterogeneity. Eligible studies included those with ≥ 4 patients treated with salvage surgery to resection of vestibular schwannomas after failure of stereotactic radiosurgery or radiotherapy.

RESULTS

Of the 1841 initially identified studies, 18 were selected, involving 455 patients, with a median follow-up of 33 months. The combined analysis showed a 69 % (CI: 58 % - 79 %) rate of good clinical outcomes. Regarding partial resection, the pooled analysis confirmed a 48 % rate (CI: 33 % to 63 %) and a 52 % complete resection rate (CI: 37 % to 67 %). The pooled analysis confirmed a 95 % hearing preservation rate in patients undergoing the retrosigmoid approach (CI: 90 % to 100 %) and a 78 % facial nerve preservation rate (CI: 72 % to 84 %). Regarding complications, the pooled analysis confirmed a 20 % complication rate (CI: 14 % to 28 %). There were no deaths related to the procedure.

CONCLUSION

Based on the results, our meta-analysis identified that rescue surgery has been shown to be safe and effective for resection of vestibular schwannomas after failure of stereotactic radiosurgery or radiotherapy, based on good facial nerve preservation rate and total lesion resection rate.

A single-cell atlas of Schwannoma across genetic backgrounds and anatomic locations

BACKGROUND

Schwannomas are nerve sheath tumors arising at cranial and peripheral nerves, either sporadically or in patients with a schwannomatosis-predisposition syndrome. There is limited understanding of the transcriptional heterogeneity of schwannomas across genetic backgrounds and anatomic locations.

METHODS

Here, we prospectively profile by single-cell full-length transcriptomics tumors from 22 patients with NF2-related schwannomatosis, non-NF2-related schwannomatosis, and sporadic schwannomas, resected from cranial and peripheral nerves. We profiled 11,373 cells (after QC), including neoplastic cells, fibroblasts, T cells, endothelial cells, myeloid cells, and pericytes.

RESULTS

We characterize the intra-tumoral genetic and transcriptional heterogeneity of schwannoma, identifying six distinct transcriptional metaprograms, with gene signatures related to stress, myelin production, antigen presentation, interferon signaling, glycolysis, and extracellular matrix. We demonstrate the robustness of our findings with analysis of an independent cohort.

CONCLUSIONS

Overall, our atlas describes the spectrum of gene expression across schwannoma entities at the single-cell level and will serve as an important resource for the community.

Repeat stereotactic radiosurgery for progressive vestibular schwannomas after primary gamma knife radiosurgery

PURPOSE

Limited data provides guidance on the management of vestibular schwannomas (VSs) that have progressed despite primary Gamma Knife radiosurgery (GKRS). The present article reports our long-term experience after repeat GKRS for VS with sustained progression after solely primary GKRS management.

METHODS

A retrospective review of 1997 patients managed between 1987 and 2023 was conducted. Eighteen patients had sustained tumor progression after primary GKRS and underwent repeat GKRS. The median repeat GKRS margin dose was 11 Gy (IQR: 11-12), the median tumor volume was 2.0 cc (IQR: 1.3-6.3), and the median cochlear dose in patients with preserved hearing was 3.9 Gy (IQR: 3-4.1). The median time between initial and repeat GKRS was 65 months (IQR: 38-118).

RESULTS

The median follow-up was 70 months (IQR: 23-101). After repeat GKRS, two patients had further tumor progression at 4 and 21 months and required partial resection of their tumors. The 10-year actuarial tumor control rate after repeat GKRS was 88%. Facial nerve function was preserved in 13 patients who had House-Brackmann grade 1 or 2 function at the time of repeat GKRS. Two patients with serviceable hearing preservation (Gardner-Robertson grade 1 or 2) at repeat GKRS retained that function afterwards. In patients with tinnitus, vestibular dysfunction, and trigeminal neuropathy, symptoms remained stable or improved for 16/16 patients, 12/15 patients, and 10/12 patients, respectively. One patient developed facial twitching in the absence of tumor growth 21 months after repeat GKRS.

CONCLUSIONS

Repeat GKRS effectively controlled tumor growth and preserved cranial nerve outcomes in most patients whose VS had sustained progression after initial primary radiosurgery.

Surgical and radiosurgical outcomes for Koos grade 3 vestibular schwannomas

This study aimed to reveal the preferred initial treatment for Koos grade 3 vestibular schwannomas (VS). We performed a two-institutional retrospective study on 21 patients with Koos grade 3 VS undergoing resection at Yokohama Medical Center and 37 patients undergoing radiosurgery at Yokohama Rosai Hospital from 2010 to 2021. Tumor control, complications, and functional preservation were compared. The median pre-treatment volume and follow-up duration were 2845 mm3 and 57.0 months, respectively, in the resection group and 2127 mm3 and 81.7 months, respectively, in the radiosurgery group. In the resection group, 16 (76.2%) underwent gross total resection, and three patients (14.3%) experienced regrowth; however, no one required additional treatment. In the radiosurgery group, the tumor control rate was 86.5%, and three cases (8.1%) required surgical resection because of symptomatic brainstem compression. Kaplan-Meier analyses revealed that tumors with delayed continuous enlargement and large thin-walled cysts were significantly associated with poor prognostic factors (p = 0.0027, p < 0.001). The pre-radiosurgery growth rate was also associated with the volume increase (p = 0.013). Two cases (9.5%) required additional operation due to complications such as post-operative hematoma and cerebrospinal fluid leaks in the resection group, whereas temporary cranial neuropathies were observed in the radiosurgery group. Two patients (9.5%) had poor facial nerve function (House-Brackmann grading grade 3) in the resection group, while no one developed facial paresis in the radiosurgery group. Trigeminal neuropathy improved only in the resection group.Radiosurgery can be considered for the treatment of Koos grade 3 VS for functional preservation. However, resection may also be considered for patients with severe trigeminal neuropathy or a high risk of volume increments, such as large thin-walled cysts and rapid pre-treatment growth.

Planned Subtotal Resection following Stereotactic Radiosurgery of Koos 3 and 4 Vestibular Schwannomas

Background/Objectives: Surgical resection of medium to large vestibular schwannomas (VSs, Koos grade 3 and 4) is a widely used approach, although stereotactic radiosurgery (SRS) is increasingly proposed as initial treatment. The quality of life-centered approach is challenged in cases where tumor growth control cannot be achieved with SRS, thus necessitating salvage surgery. We present a series of eight consecutive patients who required surgery due to continued tumor growth after SRS. Methods: Of the 146 patients with VS grades 3 and 4 initially treated with SRS, only eight patients (mean age, 54 ± 7.2 years; range, 42-63 years) required subsequent surgery. Their mean tumor volume was 9.9 ± 3.2 cm3. The mean time from SRS to first tumor progression and planned subtotal resection was 23 ± 5.9 months and 45 ± 17.5 months, respectively. SRS was not performed after the surgery in favor of a "wait and rescan" approach. Tumor residue was monitored on follow-up magnetic resonance imaging. In all patients, tumor growth control after planned subtotal resection was maintained at 63 ± 19.8 months. Results: None of the 146 patients had serious complications after SRS. In the eight patients who required surgery, tumor growth between 22% and 212% (mean, 4 cm3) was reported within 26 to 84 months after SRS. Before salvage surgery, they scored 1 point on the House-Brackmann scale. Subtotal excision was performed, and VIIth nerve function was preserved in all patients. At 63 ± 19.8 months, 3 patients had a House-Brackmann score of 1, four patients had a score of 2, and one patient had a score of 3. Conclusions: Surgical excision of medium to large VS after SRS can be relatively safe, provided that a quality of life-centered approach of subtotal resection is used.

Cystic recurrence of vestibular schwannoma post-radiosurgery: an institutional experience

BACKGROUND

Stereotactic radiosurgery effectively controls vestibular schwannoma (VS). However, in certain cases, microsurgical resection may be necessary for post-radiosurgery tumour progression. The characteristics and microsurgical challenges of uncommon cystic recurrences post-radiosurgery are rarely addressed.

METHOD

We retrospectively analysed 24 consecutive patients who underwent microsurgical intervention for recurrent VS post-radiosurgery by the senior author.

RESULTS

Tumour recurrence post-radiosurgery occurred as solid growth in 19 patients (79%), while 5 patients (21%) developed large brainstem-compressing cysts. The median time interval for tumour recurrence post-radiosurgery was similar between cystic and non-cystic recurrent VS (30 vs. 25 months; p=0.08). Cystic recurrences occurred in primarily cystic VS in 3 patients, and new cysts developed in 2 patients with primarily solid VS. Intra-operatively, tumours were firm in 18 cases (75%) and strongly adhered to surrounding structures in 14 cases (58%). All cystic cases underwent cyst decompression, while complete resection of solid tumour components was avoided due to neurovascular adherence. At a mean follow-up of 42±39 months, 12 patients (50%) showed contrast-enhancing tumour residuals in follow-up imaging, including all cystic recurrent cases. Tumour residuals remained stable without requiring further intervention, except for one patient revealing malignant tumour transformation. House-Brackmann grade I/II was preserved in 15 patients (62%). Three patients (13%) developed new facial palsy, and two patients (8%) improved to House-Brackmann grade II. Cystic recurrences had a significantly higher frequency of tumour residuals compared to solid recurrences (100% vs. 37%; p=0.01) but similar rates of facial palsy (60% vs. 32%; p=0.24) CONCLUSIONS: Cyst development in VS post-radiosurgery is more common in primary cystic lesions but can also occur in rare cases of primary solid VS. Symptomatic cysts require microsurgical decompression. However, complete resection of the solid tumour component is not crucial for long-term tumour control and should be avoided if it risks neurological function in this delicate area.

Fate of Residual Tumor After Subtotal Resection of a Previously Irradiated Vestibular Schwannoma: Long-Term Follow-Up of a Single-Institutional Series

BACKGROUND

The fate of residual tumor after salvage surgery for recurrent vestibular schwannoma (VS) after radiosurgery has not been elucidated so far. We reviewed our surgical series of salvage surgery for recurrent VS, with focus on the natural history of the residual tumor after salvage surgery.

METHODS

This study enrolled 14 patients who underwent salvage surgical resection in our institute and were followed up for >12 months.

RESULTS

The study included 3 men and 11 women with a median age of 55 years (range: 16-70 years). The median pre-stereotactic radiosurgery tumor volume was 6591 mm³. All patients were treated using gamma knife radiosurgery. The median duration from gamma knife radiosurgery to surgery was 52 months (range: 10-116 months). Solid tumor growth and cyst formation were observed in 6 (42.9%) and 8 (57.1%) patients, respectively. Subtotal resection and partial resection were performed in 13 (92.8%) patients, and gross total resection was achieved in only one (7.2%) patient. Postoperative facial paresis and surgical complication occurred in 5 (35.7%) and 2 (14.3%) patients, respectively. After salvage resection for irradiated VS, no patient showed tumor progression or recurrence during the follow-up period (13 subtotal/partial resections and 1 total resection). In addition, 2 patients in the subtotal resection group showed residual tumor shrinkage after salvage surgery during the follow-up period.

CONCLUSIONS

The behavior of residual tumors after salvage surgery for irradiated VS was stable. Adjuvant treatment for these residual tumors may not be necessary.

Understanding the Radiobiology of Vestibular Schwannomas to Overcome Radiation Resistance

Vestibular schwannomas (VS) are benign tumors arising from cranial nerve VIII that account for 8-10% of all intracranial tumors and are the most common tumors of the cerebellopontine angle. These tumors are typically managed with observation, radiation therapy, or microsurgical resection. Of the VS that are irradiated, there is a subset of tumors that are radioresistant and continue to grow; the mechanisms behind this phenomenon are not fully understood. In this review, the authors summarize how radiation causes cellular and DNA injury that can activate (1) checkpoints in the cell cycle to initiate cell cycle arrest and DNA repair and (2) key events that lead to cell death. In addition, we discuss the current knowledge of VS radiobiology and how it may contribute to clinical outcomes. A better understanding of VS radiobiology can help optimize existing treatment protocols and lead to new therapies to overcome radioresistance.

Resection of vestibular schwannomas after stereotactic radiosurgery: a systematic review

OBJECTIVE

Multiple short series have evaluated the efficacy of salvage microsurgery (MS) after stereotactic radiosurgery (SRS) for treatment of vestibular schwannomas (VSs); however, there is a lack of a large volume of patient data available for interpretation and clinical adaptation. The goal of this study was to provide a comprehensive review of tumor characteristics, management, and surgical outcomes of salvage of MS after SRS for VS.

METHODS

The Medline/PubMed, Scopus, CINAHL, Cochrane Library, and Google Scholar databases were queried according to PRISMA guidelines. All English-language and translated publications were included. Studies lacking adequate study characteristics and outcomes were excluded. Cases involving neurofibromatosis type 2, previous MS, or malignant transformation were excluded when possible.

RESULTS

Twenty studies containing 297 cases met inclusion criteria. Three additional cases from Rush University Medical Center were added for 300 total cases. Tumor growth with or without symptoms was the primary indication for salvage surgery (92.3% of cases), followed by worsening of symptoms without growth (4.6%) and cystic enlargement (3.1%). The average time to MS after SRS was 39.4 months. The average size and volume of tumor at surgery were 2.44 cm and 5.92 cm3, respectively. The surgical approach was retrosigmoid (42.8%) and translabyrinthine (57.2%); 59.5% of patients had a House-Brackmann (HB) grade of I or II. The facial nerve was preserved in 91.5% of cases. Facial nerve preservation and HB grades were lower for the translabyrinthine versus retrosigmoid approach (p = 0.31 and p = 0.18, respectively); however, fewer complications were noted in the translabyrinthine approach (p = 0.29). Gross-total resection (GTR) was completed in 55.7% of surgeries. Studies that predominantly used subtotal resection (STR) were associated with a lower rate of facial nerve injury (5.3% vs 11.3%, p = 0.07) and higher rate of HB grade I or II (72.9% vs 48.0%, p = 0.00003) versus those using predominantly GTR. However, majority STR was associated with a recurrence rate of 3.6% as compared to 1.4% for majority GTR (p = 0.29).

CONCLUSIONS

This study showed that the leading cause of MS after SRS was tumor growth at an average of 39.4 months after radiation. There were no significant differences in outcomes of facial nerve preservation, postoperative HB grade, or complication rate based on surgical approach. Patients who underwent STR showed statistically significant better HB outcomes compared with GTR. MS after SRS was considered by most authors to be more difficult than primary MS. These data support the notion that the surgical goals of salvage surgery are debulking of tumor mass, decreasing compression of the brainstem, and not necessarily pursuing GTR.

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

BACKGROUND AND OBJECTIVE

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSION

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

Strain stiffening of peripheral nerves subjected to longitudinal extensions in vitro

The mechanical response of peripheral nerves is crucial to understand their physiological and pathological conditions. However, their response to external mechanical solicitations is still partially unclear, since peripheral nerves could behave in a quite complex way. In particular, nerves react to longitudinal strains increasing their stiffness to keep axons integrity and to preserve endoneural structures from overstretch. In this work, the strain stiffening of peripheral nerves was investigated in vitro through a recently introduced computational framework, which is able to theoretically reproduce the experimental behaviour of excised tibial and sciatic nerves. The evolution and the variation of the tangent modulus of tibial and sciatic nerve specimens were quantitatively investigated and compared to explore how stretched peripheral nerves change their instantaneous stiffness.

Facial nerve outcome and extent of resection in cystic versus solid vestibular schwannomas in radiosurgery era

OBJECTIVE Cystic vestibular schwannomas (CVSs) are a subgroup of vestibular schwannomas (VSs) that are reported to be associated with unpredictable clinical behavior and unfavorable postoperative outcomes. The authors aimed to review their experience with microsurgical treatment of CVSs in terms of extent of resection and postoperative facial nerve (FN) function and compare these outcomes with those of their solid counterparts. METHODS Two hundred-eleven VS patients were treated surgically between 2006 and 2017. Tumors were defined as cystic when preoperative neuroimaging demonstrated cyst formation that was confirmed by intraoperative findings. Solid VS (SVSs) with similar classes were used for comparison. Clinical data of the patients were reviewed retrospectively, including clinical notes and images, as well as operative, pathology, and neuroradiology reports. RESULTS Thirty-two patients (20 males and 12 females) with a mean age of 52.2 years (range 17-77 years) underwent microsurgical resection of 33 CVSs (mean size 3.6 cm, range 1.5-5 cm). Forty-nine patients (26 males and 23 females) with a mean age of 49.9 years (range 21-75 years) underwent microsurgical resection of 49 SVSs (mean size 3 cm, range 2-4.5 cm). All operations were performed via either a retrosigmoid or a translabyrinthine approach. Gross-total resection was achieved in 30 cases in the CVS group (90.9%) and 37 in the SVS group (75.5%). The main reason for subtotal and near-total resection was adherence of the tumor to the brainstem and/or FN in both groups. None of the patients with subtotal or near-total resection in the CVS group demonstrated symptomatic regrowth of the tumor during the mean follow-up period of 41.6 months (range 18-82 months). The FN was anatomically preserved in all patients in both groups. Good FN outcomes were achieved in 15 of CVS (grade I-II; 45.5%) and 35 of SVS (71.4%) surgeries at discharge. Good and fair FN functions were noted in 22 (grade I-II; 81.5%) and 5 (grade III only; 18.5%) of the CVS patients, respectively, at the 1-year follow-up; none of the patients showed poor FN function. CONCLUSIONS Surgery of CVSs does not necessarily result in poor outcomes in terms of the extent of resection and FN function. Special care should be exercised to preserve anatomical continuity of the FN during surgery, since long-term FN function outcomes are much more satisfactory than short-term results. High rates of gross-total resection and good FN outcomes in our study may also suggest that microsurgery stands as the treatment of choice in select cases of large CVSs and SVSs in the era of radiosurgery.

Stereotactic Radiosurgery for Cystic Vestibular Schwannomas

BACKGROUND

The optimum treatment for cystic vestibular schwannoma (VS) remains controversial. Anecdotally, many treating physicians feel that cystic VSs do not respond to stereotactic radiosurgery (SRS) as well as noncystic tumors.

OBJECTIVE

To present outcomes after treatment of predominantly cystic VS with SRS.

METHODS

A prospectively maintained clinical database of patients undergoing Gamma Knife (Elekta Instruments, Stockholm, Sweden) radiosurgery (GKRS) for VS at a single tertiary academic referral center was retrospectively reviewed. Patients diagnosed with cystic VS who were treated with GKRS between 1997 and 2014 were analyzed. Size-matched solid tumors treated with GKRS during this period were selected as controls.

RESULTS

Twenty patients (12 women; median age at treatment, 56 years; range, 36-85 years) with cystic VS met inclusion criteria. The median radiologic follow-up within the cystic group was 63 months (range, 17-201 months), and the median change in tumor size was -4.9 mm (range, -10.4 to 9.3 mm). Sixteen tumors (80%) shrank, 2 (10%) remained stable, and 2 (10%) enlarged, accounting for a tumor control rate of 90%. The median radiologic follow-up in the noncystic control group was 67 months (range, 6-141 months), and the median change in size was -2.0 mm (range, -10.4 to 2.5 mm). Tumor control in the solid group was 90%. Comparing only those tumors that decreased in size showed that there was a trend toward a greater reduction within the cystic group ( P = .05).

CONCLUSION

The present study demonstrates that tumor control after SRS for cystic VS may not differ from that of noncystic VS in selected cases.

Quality of life in patients with unilateral vestibular schwannoma on wait and see - strategy

OBJECTIVE

A 'wait and see' strategy is an option when managing patients with small vestibular schwannomas (VS). A risk of growth and worsening of hearing may influence a patient's daily quality of life (QOL). Therefore, the present study focused on QOL parameters in patients who are on a 'wait and see' strategy following magnetic resonance imaging (MRI)-based diagnosis of small unilateral VS.

PATIENTS AND METHODS

Sixty-five patients (mean age 64.4 years; male:female, 32:33) who suffered from a small unilateral VS (9.34 mm, range 1.5-23 mm) between 2013 and 2016 were included in a prospective single center study. During follow-up, in addition to clinical and neurological examinations and MRI imaging, all patients answered the Short Form 36 questionnaire once to characterize QOL. Additionally, the severity of tinnitus was determined by the Mini-TQ-12 from Hiller and Goebel.

RESULTS

It was found during follow-up that there was no lowering of QOL in patients with small VS who were on 'wait and see' strategy compared with Germany's general population and no tumor growth was detected in 53 patients (81.5%). Patients with a tumor diameter larger than 10 mm did not suffer from stronger tinnitus, vertigo or unsteadiness than the group with an average tumor size, which is smaller than 10 mm. Sixty-two patients (95.4%) showed ipsilateral hearing loss and three of these reported deafness (4.6%). Severe vertigo or tinnitus is connected with lower levels of mental component scale and physical component scale. These findings reduced the QOL (p = 0.05).

CONCLUSION

In our series, QOL is not influenced in patients with unilateral untreated small VS in comparison to Germany's general population. This is helpful information when advising patients during follow-up and finding out the optimal timing of individual treatment.