The object of this study was to evaluate the natural history, pattern, and occurrence of tumor growth and its consequences for treatment of small-sized vestibular schwannomas (VSs).
From 1990 to 2005, 386 patients underwent conservative management for VS because of the following: age > 60 years, poor health/medical risks, risk of deterioration of good hearing, small tumor size, minimal or no incapacitating symptoms, and/or patient preference. Tumor size was measured by MR imaging according to the guidelines of the Committee on Hearing and Equilibrium. The first MR imaging study was performed 1 year after diagnosis, and subsequent imaging was performed yearly or every 2 years depending on the appearance of new symptoms, tumor growth, or both.
Sixty-one patients were lost to follow-up the first year after presentation. Of the 325 patients for whom 1-year follow-up data were available, 39 showed tumor growth ≥ 3 mm. Conservative management was discontinued for these 39 patients. The patients who returned for follow-up were evaluated at 1- or 2-year intervals depending on tumor growth. The authors extrapolated to obtain data for 2-year intervals, yielding data for 160, 56, 21, and 8 patients at 3, 5, 7, and 9 years after initial presentation, respectively. The overall mean tumor growth rate (±standard deviation) was 1.15 ± 2.4 mm/year. This rate was estimated by pooling all values of tumor growth that had been determined for all patients and dividing by the total number of “events,” with each assessment constituting an event. In 58.6% of patients, the annual tumor growth rate was < 1 mm/year; in 29.2%, 1–3 mm/year; and in 12.2%, ≥ 3 mm/ year. The growth rates of intrameatal (1.02 ± 1.8 mm/year) and extrameatal (1.40 ± 3.1 mm/year) tumors did not differ significantly. No significant association was found between tumor growth rate and sex, age, initial hearing status, or initial tumor grade. Delay in diagnosis was the only significant factor associated with tumor growth rate. During follow-up, conservative management was discontinued for 77 (23.7%) of the 325 patients for whom at least 12-month follow-up data were available; surgery was performed in 60 (77.9%) and radiation therapy in 17 (22.1%).
The results of this study support the role of a conservative “wait-and-scan” policy of management for small-sized VSs because most have a slow growth rate. Long-term neuroimaging follow-up is needed even with non-growing tumors.