Volumetric growth rates of untreated vestibular schwannomas

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>There remains a large discrepancy among surgeons in expectations of vestibular schwannoma (VS) growth. The anticipated growth rate of a VS and its potential clinical impact are important factors when deciding whether to observe the lesion over time or to intervene. Previous studies of VS natural growth remain limited, mostly confined to linear measurements, often without high-resolution, thin-sequence imaging. The present study comprehensively assessed natural tumor growth rates using volumetric measurements.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>Between 2012 and 2018, 212 treatment-naïve patients diagnosed with a unilateral VS were evaluated. A total of 699 MR images were assessed, with a range of 2–11 MR images per patient. All MR images preceded any intervention, with patients subsequently being observed through completion of data analysis (36%) or treated with stereotactic radiosurgery (32%) or microsurgical resection (32%). To determine precise tumor volumes, the tumor area was outlined on every slice, and the products of the area and slice thickness were summed (99% of scans were ≤ 1-mm slice thickness). A multilevel model with random effects was used to assess the mean volume change over time. Each tumor was categorized as one of the following: growing (volume increase by more than 20% per year), fast growing (volume increase by more than 100% per year), stable (volume change between 20% decrease and 20% increase per year), and shrinking (volume decrease by more than 20% per year).</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>The mean VS volumetric growth rate was 33.5% per year (95% CI 26.9%–40.5%, p &lt; 0.001). When assessing the frequencies of individual tumor annual growth rates, 66% demonstrated growth (30% fast growing), 33% were stable, and 1% exhibited shrinking over an average interval of 25 months. Larger tumors were associated with increased absolute growth, but there was no relationship between tumor size and proportional growth rate. There was also no relationship between patient age and tumor growth rate.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>This study comprehensively assessed VS volumetric growth rates using high-resolution images and was conducted in a large and diverse patient sample. The majority of the tumors exhibited growth, with about one-third growing at a rate of 100% per year. These findings may contribute to a consensus understanding of tumor behavior and inform clinical decisions regarding whether to intervene or observe.</jats:p></jats:sec>

Gamma knife surgery in the treatment of intracanalicular vestibular schwannomas

“…According to Stangerup et al, the likelihood of IVS growth was not associated with patient age, sex, and initial hearing status. There is growing evidence that the rate of IVS growth may strictly depend on tumor size measurement methodology; those studies utilizing the volumetric approach versus linear measurement show a much higher rate of growth—the mean VS volumetric growth rate was 33.5% per year . In accordance to Regis et al and Thomsen et al we observed similar proportion of patients presenting initial tumor growth—94 out of 141 patients (94 patients presented documented tumor growth whereas 47 patients presented no tumor growth at follow‐up visits) .…”

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

“…With a mean follow-up of 4.1 years, Lees et al [93] reported that approximately 51.2% of the extrameatal tumors showed progression (defined as ≥ 2 mm increase in tumor diameter) at a median linear diameter growth rate of 1.49 mm per year. When assessing the volumetric growth (defined as ≥ 20% increase in volume, based on literature evidence which showed that data error as high as 20% should be considered when assessing volumetric changes [126]), they found that 67.4% of the extrameatal tumor showed progression at a rate of 32.9% change in volume per year in accordance with previous reports [150,173,185]. Schnurmann et al [150] assessed tumor growth rates using volumetric measurements in 212 patients and found that 66% of the tumors demonstrated growth over an average interval of 25 months with a volumetric growth rate of 33.5% per year.…”

“…Assessing tumor growth rate may also depend on the chosen criteria for the determination of growth (largest diameter vs. volume, number of millimeters or cubic centimeters). In the Danish database, tumor growth was defined as an increase of at least 3 mm in the largest extrameatal diameter, but the adequacy of this parameter has been widely questioned since a tumor may grow along other directions and may be missed with traditional linear measurements [93,150]. With a mean follow-up of 4.1 years, Lees et al [93] reported that approximately 51.2% of the extrameatal tumors showed progression (defined as ≥ 2 mm increase in tumor diameter) at a median linear diameter growth rate of 1.49 mm per year.…”

“…In this series only 8% of the extracanalicular tumors were larger than 3 cm. Since smallmedium sized VSs represent the vast majority of the tumors analyzed in these studies, the applied tumor growth cutoffs may not be adequate for large VS for whom even a minor linear growth can result in a substantial increase in volume, considering that a 6% increase along one axis corresponds to a 20% volumetric growth in a sphere [150]. To date there is no consensus on the quantitative definition of growth in terms of linear or volumetric cutoff.…”

Association of Metformin With the Growth of Vestibular Schwannomas

“…Each electronic medical record was reviewed to determine the patient’s age, sex, hemoglobin A1c (HbA1c), and metformin, statin, or aspirin usage based on the patient’s medication profile. Per several previous reports in the literature, VS tumor growth was defined as a 20% increase in tumor volume 17-20 between consecutive MRI studies or between the first and last MRI study available, which was the primary endpoint. Tumor growth in patients who had evidence of having been prescribed any of the aforementioned medications were compared with medication nonusers.…”