Natural History of Growing Sporadic Vestibular Schwannomas During Observation: An International Multi-Institutional Study

Documented Initial Growth Does Not Necessarily Indicate Treatment for Sporadic Vestibular Schwannomas

OBJECTIVE

To report the natural history of vestibular schwannoma (VS) who elected an initial period of observation and identify prognostic factors. To describe the natural history of growing VS, identify prognostic factors, and review the most recent literature.

STUDY DESIGN

Prospective cohort study and literature review.

SETTING

Tertiary referral center.

PATIENTS

Adult patients diagnosed with a VS between January 1998 and February 2023.

INTERVENTION

Magnetic resonance imaging surveillance.

MAIN OUTCOME MEASURES

Growth-free survival and subsequent growth-free survival considering significant growth as a change in size of ≥2 mm.

RESULTS

Of 430 patients undergoing observation with serial magnetic resonance imaging, 193 (44.9%) demonstrated significant growth at a median of 1.6 years (interquartile range, 0.94-3.51). Of the 193 patients who presented an initial episode of growth, 137 elected to continue to be observed. Of those, 83 (60.6%) presented a second episode of growth at a median of 1.43 years (interquartile range, 1.00-2.49). The subsequent growth-free survival rates (95% confidence interval) at 1, 3, 5, 7, and 10 years were 91.79% (87.26-96.56%), 64.44% (56.56-73.42%), 52.52% (44.23-62.35%), 42.23% (33.92-52.56%), and 36.11% (27.89-46.76%), respectively. Univariate and multivariate Cox regression analyses showed that EC tumor location and initial growth rate were significant predictors of subsequent growth.

CONCLUSIONS

Close observation after documentation of growth is an appropriate management in well-selected cases given that only around 56% of the tumor will continue to grow. Extracanalicular tumor location and initial growth rate are promising prognostic factors to help determine which patient would be a better candidate for close surveillance after initial documentation of growth.

Salvage Microsurgery Following Failed Primary Radiosurgery in Sporadic Vestibular Schwannoma

Importance

Management of sporadic vestibular schwannoma with radiosurgery is becoming increasingly common globally; however, limited data currently characterize patient outcomes in the setting of microsurgical salvage for radiosurgical failure.

Objective

To describe the clinical outcomes of salvage microsurgery following failed primary stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) among patients with sporadic vestibular schwannoma.

Design, Setting, and Participants

This was a cohort study of adults (≥18 years old) with sporadic vestibular schwannoma who underwent salvage microsurgery following failed primary SRS/FSRT in 7 vestibular schwannoma treatment centers across the US and Norway. Data collection was performed between July 2022 and January 2023, with data analysis performed between January and July 2023.

Exposure

Salvage microsurgical tumor resection.

Main Outcomes and Measures

Composite outcome of undergoing less than gross total resection (GTR) or experiencing long-term facial paresis.

Results

Among 126 patients, the median (IQR) age at time of salvage microsurgery was 62 (53-70) years, 69 (55%) were female, and 113 of 117 (97%) had tumors that extended into the cerebellopontine angle at time of salvage. Of 125 patients, 96 (76%) underwent primary gamma knife SRS, while 24 (19%) underwent linear accelerator-based SRS; the remaining patients underwent FSRT using other modalities. Postoperative cerebrospinal fluid leak was seen in 15 of 126 patients (12%), hydrocephalus in 8 (6%), symptomatic stroke in 7 (6%), and meningitis in 2 (2%). Each 1-mm increase in cerebellopontine angle tumor size was associated with a 13% increased likelihood of foregoing GTR (64 of 102 patients [63%]) or long-term postoperative House-Brackmann grade higher than I (48 of 102 patients [47%]) (odds ratio, 1.13; 95% CI, 1.04-1.23). Following salvage microsurgery, tumor growth-free survival rates at 1, 3, and 5 years were 97% (95% CI, 94%-100%), 93% (95% CI, 87%-99%), and 91% (95% CI, 84%-98%), respectively.

Conclusions

In this cohort study, more than half of patients who received salvage microsurgery following primary SRS/FSRT underwent less than GTR or experienced some degree of facial paresis long term. These data suggest that the cumulative risk of developing facial paresis following primary SRS/FSRT by the end of the patient's journey with treatment approximates 2.5% to 7.5% when using published primary SRS/FSRT long-term tumor control rates.

Wait-and-scan management in sporadic Koos grade 4 vestibular schwannomas: A longitudinal volumetric study

Background

Volumetric natural history studies specifically on large vestibular schwannomas (VSs), commonly classified as Koos grade 4, are lacking. The aim of the current study is to present the volumetric tumor evolution in sporadic Koos grade 4 VSs and possible predictors for tumor growth.

Methods

Volumetric tumor measurements and tumor evolution patterns from serial MRI studies were analyzed from selected consecutive patients with Koos grade 4 VS undergoing initial wait-and-scan management between January 2001 and July 2020. The significant volumetric threshold was defined as a change in volume of ≥10%.

Results

Among 215 tumors with a median size (IQR) of 2.7 cm3 (1.8-4.2), 147 tumors (68%) demonstrated growth and 75 tumors (35%) demonstrated shrinkage during follow-up. Growth-free survival rates (95% CI) at 1, 2, 5, and 10 years were 55% (48-61), 36% (29-42), 29% (23-36), and 28% (21-34), respectively and did not significantly differ in tumors> 20 mm (Chi-square = .40; P-value = .53). Four tumor evolution patterns (% of total) were observed: continued growth (60); initial growth then shrinkage (7); continued shrinkage (27); and stability (5). Good hearing (adjusted HR 2.21, 95% CI 1.48-3.30; P < .001) and peritumoral edema (adjusted HR 2.22, 95% CI 1.18-4.13; P = .01) at diagnosis were significantly associated with an increased likelihood of growth.

Conclusions

Koos grade 4 VSs show a wide variety in size and growth. Due to variable growth patterns, an initial wait-and-scan strategy with short scan intervals may be an acceptable option in selected tumors, if no significant clinical symptoms of mass effect that warrant treatment are present.

Life Expectancy After Diagnosis of a Vestibular Schwannoma in Patients 70 Years and Older

Importance

Over the past decades, the number of patients, especially in the older adult patient group, diagnosed with vestibular schwannoma (VS) has increased. Assuming that older adult patients have more comorbidities, a longer recovery period after surgery, a higher rate of surgical complications, and a higher mortality rate after VS surgery, a treatment strategy for this group of patients is warranted, based on clinical evidence on postsurgical survival.

Objective

To evaluate the survival after diagnosis of a VS in patients 70 years and older, treated with either observation or surgery, and to compare these findings with the life span of an age-matched background population in Denmark.

Design, Setting, and Participants

This was a retrospective cohort study of 624 patients 70 years and older diagnosed with VS in Denmark from 1976 to 2016. Since 1976, all patients with a VS have been registered in a national database, which contains 3637 patients. Of the included patients in this study, 477 were treated conservatively with the "wait-and-scan" strategy, and 147 were treated surgically with removal of the tumor. The survival of the patients was compared with a matched background population in Denmark. Data analysis was performed from January 1976 to January 2017.

Exposures

Surgery, radiotherapy, or none.

Main Outcomes and Measures

The main outcome was survival among the patients and compared with the matched background population.

Results

A total of 624 patients were included (317 female patients [50.8%] and 307 male patients [49.2%]). The mean (SD) survival in the observed patients was 9.2 (4.7) years after diagnosis, whereas for the background population, the expected survival was 11 years from the mean age at diagnosis. For the surgically treated patients, the mean (SD) survival was 11.8 (6.6) years, and expected survival was 11 years for the matched background population. The mean (SD) survival was 10.7 (5.5) years in female patients and 8.9 (5.0) years in male patients. There was no significant difference in survival between treatment modalities, irrespective of tumor size.

Conclusions and Relevance

In this cohort study, survival after diagnosis of a VS in patients 70 years and older was similar in the surgical group compared with the age-matched background population. In the wait-and-scan group, the survival after diagnosis was marginally shorter, which may be associated with increased comorbidity.

Comparing Linear and Volumetric Tumor Measurements During Observation of Growing Sporadic Vestibular Schwannomas

OBJECTIVE

To assess the correlation between linear and volumetric changes in vestibular schwannomas (VS).

STUDY DESIGN

Retrospective imaging review was performed on patients diagnosed with sporadic VS from 2000 to 2019 who demonstrated linear growth on observation with serial magnetic resonance imaging (MRI).

SETTING

Two large tertiary care centers.

METHODS

Changes in diameter on serial MRI scans, measured by 1995 American Academy of Otolaryngology-Head and Neck Surgery guidelines, were compared to changes in volume, calculated by segmentation.

RESULTS

Ninety-two patients had VS confined to the internal auditory canal (IAC) with 236 MRIs analyzed, and 108 patients had VS involving the cerebellopontine angle (CPA) with 193 MRIs analyzed. The Spearman rank correlation coefficients between changes in diameter and volume for IAC and CPA tumors were 0.43 (p < .001) and 0.65 (p < .001), respectively. Linear diameter increases of 1 to <2 mm corresponded to a median volume change of 32% (interquartile range [IQR]: 6%-86%) for IAC tumors, compared to 23% (IQR: 13%-40%) for CPA tumors. Linear diameter increases of 2 to <3 mm (ie, the minimum linear diameter change classically considered "true growth") corresponded to a median volume change of 42% (IQR: 23%-100%) and 47% (IQR: 26%-69%) for IAC and CPA tumors, respectively.

CONCLUSION

Changes in linear diameter significantly correlated with changes in volume for IAC and CPA tumors, although diameter changes that did not meet the definition of linear growth (<2 mm) had corresponding median volume changes in excess of 20% for both IAC and CPA tumors.

Presbycusis and Hearing Preservation in Observed Vestibular Schwannomas

OBJECTIVE

We reviewed a cohort of patients with untreated sporadic vestibular schwannoma (VS) and examined the relationship between high-frequency hearing loss (HFHL) in the non-VS ear and long-term hearing outcomes in the VS-affected ear. We hypothesized that the progression of HFHL is associated with accelerated hearing decline in sporadic VS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary center.

PATIENTS

We studied 102 patients with sporadic VS diagnosed from 1999 to 2015 with ≥5 years of observation (median, 6.92; interquartile range, 5.85-9.29). Sixty-six patients had AAO-HNS class A/B hearing at presentation and were included in analysis.

INTERVENTIONS

Audiometry, serial magnetic resonance imaging for observation of VS.

MAIN OUTCOME MEASURES

Four-frequency pure tone average (PTA) and word recognition scores (WRS) in the VS-affected ear. Decline in high-frequency PTA (average of thresholds at 4000, 6000, and 8,000 Hz) was defined as ≥10 dB during the study period. Decline in WRS was defined as ≥10%.

RESULTS

Compared with those without, patients with progressive HFHL in the non-VS ear were more likely to experience a decline in WRS in the VS ear (80% vs. 54%, p = 0.031). However, the same group showed no difference (52% vs. 41%, p = 0.40) in decline in PTA of the VS ear.

CONCLUSIONS

Patients with observed VS who experience progressive HFHL in the non-VS ear are more likely to experience significant declines in speech understanding in the VS-affected ear over time. Patients with a history of presbycusis may have an increased risk of losing serviceable hearing because of sporadic VS.

The Effect of Metformin on Vestibular Schwannoma Growth: A Systematic Review and Meta-analysis

OBJECTIVES

To systematically review and evaluate metformin's potential impact on vestibular schwannoma (VS) growth.

DATA SOURCES

PubMed, Cochrane Library, and Embase.

REVIEW METHODS

A retrospective cohort study was performed on sporadic VS patients undergoing initial observation who had at least two magnetic resonance imaging studies. Patients were stratified by metformin use during the observation period. Primary endpoint was VS growth, defined as at least a 2 mm increase in diameter. Survival free of tumor growth was evaluated between groups. Systematic review and meta-analysis were performed to produce a pooled odds ratio [OR]. Study heterogeneity was assessed and post-hoc power analysis was performed.

RESULTS

A total of 123 patients were included, of which 17% were taking metformin. Median patient age was 56.6 years (range, 25.1-84.5). There were no statistically significant differences between the groups. Survival analysis did not demonstrate a statistically significant difference in time to VS growth between groups (hazard ratio = 0.61, 95% confidence interval [CI] = 0.29-1.29). Furthermore, logistic regression analysis did not demonstrate a statistically significant difference between groups in the odds of VS growth (OR = 0.46, 95% CI = 0.17-1.27). Systematic review identified 3 studies. Meta-analysis suggested that metformin reduces the odds of developing VS growth (pooled OR = 0.45, 95% CI = 0.29-0.71). Studies demonstrated low between-study heterogeneity. Power analysis demonstrated a sample size of 220 patients with equal randomization would be required to prospectively identify a true difference with 80% power.

CONCLUSIONS

Metformin use may reduce the odds of VS growth. A randomized trial would be ideal to identify an unbiased estimate of metformin's effect on VS growth. Laryngoscope, 133:2066-2072, 2023.

Introducing an Evidence-Based Approach to Wait-And-Scan Management of Sporadic Vestibular Schwannoma

The advent of MRI has led to more sporadic vestibular schwannomas diagnosed today than ever before. Despite the average patient being diagnosed in their sixth decade of life with a small tumor and minimal symptoms, population-based data demonstrate that more tumors per capita are treated today than ever before. Emerging natural history data justify either an upfront treatment approach or the "Size Threshold Surveillance" approach. Specifically, if the patient elects to pursue observation, then existing data support the tolerance of some growth during observation in appropriately selected patients up until a specific size threshold range (about 15 mm of CPA extension). The current article discusses the rationale behind a shift in the existing observation management approach, where initial detection of growth typically begets treatment, and outlines the application of a more flexible and nuanced approach based on existing evidence.

How many growing vestibular schwannomas tend to stop growing without any treatment?

OBJECTIVE

To determine the long-term, spontaneous growth arrest rates in a large cohort of vestibular schwannoma patients.

METHODS

This paper describes a retrospective case series of 735 vestibular schwannoma patients organised into four groups: group A patients showed tumour growth which then stopped without any treatment; group B patients showed tumour growth which continued, but were managed conservatively; group C patients had a growing vestibular schwannoma and received active treatment; and group D patients had a stable, non-growing vestibular schwannoma. Demographics, tumour size and vestibular schwannoma growth rate (mm/month) were recorded.

RESULTS

A total of 288 patients (39.2 per cent) had growing vestibular schwannomas. Of the patients, 103 (35.8 per cent) were managed conservatively, with 52 patients (50.5 per cent of the conservative management group, 18 per cent of the total growing vestibular schwannoma group) showing growth arrest, which occurred on average at four years following the diagnosis. Eighty-two per cent of vestibular schwannomas stopped growing within five years. Only differences between age (p = 0.016) and vestibular schwannoma size (p = 0.0008) were significant.

CONCLUSION

Approximately 20 per cent of growing vestibular schwannomas spontaneously stop growing, predominantly within the first five years; this is important for long-term management.

Spontaneous Volumetric Tumor Regression During Wait-and-Scan Management of 952 Sporadic Vestibular Schwannomas

OBJECTIVE

Spontaneous tumor shrinkage during wait-and-scan management of sporadic vestibular schwannoma is generally considered an uncommon phenomenon. However, most data informing this understanding stem from single-slice linear tumor measurements taken in the axial imaging plane. The objective of the current work was to characterize the regression capacity of sporadic vestibular schwannomas using volumetric tumor measurements.

STUDY DESIGN

Retrospective cohort study using slice-by-slice, three-dimensional volumetric tumor measurements.

SETTING

Three tertiary referral centers.

PATIENTS

Patients with sporadic vestibular schwannoma.

INTERVENTIONS

Wait-and-scan.

MAIN OUTCOME MEASURES

Regression-free survival rates with regression defined as a decrease of at least 20% of the tumor volume.

RESULTS

Among 952 patients undergoing a total of 3,505 magnetic resonance imaging studies during observation, 123 experienced volumetric tumor regression after diagnosis at a median of 1.2 years (interquartile range, 0.6-2.9 yr). Volumetric regression-free survival rates (95% confidence interval; number still at risk) at 1, 3, and 5 years after diagnosis were 94% (92-95%; 662), 86% (83-89%; 275), and 78% (73-82%; 132), respectively. Among 405 patients who demonstrated an initial period of tumor growth but continued wait-and-scan management, 48 experienced volumetric regression at a median of 1.2 years (interquartile range, 0.8-2.6 yr) after initial growth. Volumetric regression-free survival rates at 1, 3, and 5 years after initial growth were 94% (92-97%; 260), 84% (79-89%; 99), and 75% (67-83%; 43), respectively. Ultimately, only 82 of the 952 patients studied showed exclusively volumetric tumor regression (i.e., without any periods of tumor growth) by the time of last follow-up.

CONCLUSION

Spontaneous volumetric tumor shrinkage during wait-and-scan management occurs more frequently than suggested by previous studies using linear tumor measurements and can even occur after previous episodes of documented tumor growth. These data further highlight the dynamic nature of vestibular schwannoma growth. To this end, the application of natural history data to patient management requires a nuanced approach that parallels the complex tumor behavior of vestibular schwannoma.

Long-term natural history and patterns of sporadic vestibular schwannoma growth: A multi-institutional volumetric analysis of 952 patients

BACKGROUND

The current study aims to characterize the natural history of sporadic vestibular schwannoma volumetric tumor growth, including long-term growth patterns following initial detection of growth.

METHODS

Volumetric tumor measurements from 3505 serial MRI studies were analyzed from unselected consecutive patients undergoing wait-and-scan management at three tertiary referral centers between 1998 and 2018. Volumetric tumor growth was defined as a change in volume ≥20%.

RESULTS

Among 952 patients undergoing observation, 622 experienced tumor growth with initial growth-free survival rates (95% CI) at 1, 3, and 5 years following diagnosis of 66% (63-69), 30% (27-34), and 20% (17-24). Among 405 patients who continued to be observed despite demonstrating initial growth, 210 experienced subsequent tumor growth with subsequent growth-free survival rates at 1, 3, and 5 years following initial growth of 77% (72-81), 37% (31-43), and 24% (18-31). Larger tumor volume at initial growth (HR 1.13, P = .02) and increasing tumor growth rate (HR 1.31; P < .001) were significantly associated with an increased likelihood of subsequent growth, whereas a longer duration of time between diagnosis and detection of initial growth was protective (HR 0.69; P < .001).

CONCLUSIONS

While most vestibular schwannomas exhibit an overall propensity for volumetric growth following diagnosis, prior tumor growth does not perfectly predict future growth. Tumors can subsequently grow faster, slower, or demonstrate quiescence and stability. Larger tumor size and increasing tumor growth rate portend a higher likelihood of continued growth. These findings can inform timing of intervention: whether upfront at initial diagnosis, after detection of initial growth, or only after continued growth is observed.