Abstract
BACKGROUND
Review of SRT for vestibular schwannoma (VS) within Wessex region led by University Hospital Southampton (UHS). UHS treat tumour volumes max 2.5cm in diameter without brainstem compression with 21Gy/3#. We reviewed the experience of local control and toxicity profile in our centre comparing with 1 and 5 fraction SRT schedules. We present three fraction SRT as an appropriate fractionation schedule.
MATERIAL AND METHODS
This is a retrospective analysis of patients treated for radiologically diagnosed vestibular schwannoma from 2019 to present. Patient notes, audiograms, imaging and radiotherapy planning system were reviewed for data collection. No patients were removed from analysis due to missing data.
RESULTS
84 patients have been treated with SRT for VS. Median age 66 (39-94). 12Gy/1# (1#) in 36 patients, 21Gy/3# (3#) in 36 patients, 25Gy/5# (5#) in 12 patients. In the 1# group PTV volume 0.31cm3-4.44cm3 (median 1.12cm3), in the 3# group PTV volume from 1.03cm3 to 5.52cm3 (median 2.37cm3), in the 5# group 2.05cm3-5.44cm3 (median 4.12cm3). All patients have radiologically stable disease to date. Objective radiological response noted in 14 patients (38.9%) in 3# group this is higher than any other group and statistically significant (p=0.016). Pre-treatment serviceable hearing only in a minority of patients. Treatment related toxicity was seen in 27% in the 1# group, 19% of patients within the 3# group, and 33% in the 5# group. This was mostly mild and self-limiting. Facial nerve toxicity was seen in 8.3% of the 1# group, 16.7% of 3# group, and 33.3% of the 5# group. However, this was only persistent in 2 patients in 1# group (5.6%), 2 patients in the 3# group (5.6%), and 1 (8.3%) in the 5# group. There is no statistical difference in toxicity between any group using Chi squared test. In 3# group, when Dmax limited to <26Gy (n=15), the frequency of facial nerve toxicity reduces to 1 (2.78%).
CONCLUSION
Three fraction SRT provides excellent local control with high levels of objective radiological response in tumours up to 4cm3, however, long term follow-up is required. This treatment has acceptable toxicity which is not significantly different from alternative fractionation schedules and is improved by limiting Dmax to <26Gy.