In Growing Vestibular Schwannomas: Growth Comparison between Untreated Patients and Those Treated with Stereotactic Radiosurgery

Stereotactic RadioSurgery (SRS) is a well recognized treatment used mainly for growing or medium-sized Vestibular Schwannomas (VS). Quantifying the effect of SRS on the natural history of VS growth is difficult. Most VS will respond positively to SRS, however it is also known that some VS will spontaneously stop growing or regress. The aim of this study was to compare the growth patterns in patients with growing or medium sized VS untreated and treated with SRS. A retrospective analysis of all patients with VS managed in a tertiary referral center was performed. The computerised Radiology imaging System was used to analyze the Magnetic Resonance Imaging(MRI) of all patients. The tumor was measured in 3 planes on axial and coronal contrast-T1-weighted MRI to calculate tumor volume. Significant change in size was deemed as a change of greater than 15%. Patients with insufficient scans to confirm tumor growth pre SRS or less than 2 years follow up post SRS were excluded along with patients with NF2 or where MRI images were not available. Growth patterns in the first 2 years following diagnosis were used to confirm growing or not growing VS. Those treated with SRS were then compared with those not treated. In a 10 year period 593 patients with VS were identified and 163 of these were excluded. In the untreated group 63 patients had no growth or regression in the first 2 years (13 went on to have growth at a later stage). Forty-one patients showed evidence of growth in the first 2 years and of these 23 (56%) showing evidence of growth beyond 2 years. Fifty-five growing VS received SRS, however only forty patients have greater than 2 year follow up post SRS along with serial scans pre SRS. Twenty two (54%) of those treated, decreased in size, 9 (23%) did not change and 9 (23%) increased in size post SRS. Of the 9 that increased in size, tumor control was still managed in 7. This study suggests that SRS has a significant negative effect growth patterns of VS, however in this study the treated group tended to contain larger VS than the untreated group.