ESTRO 2024 - Abstract Book

S952

Clinical - CNS

ESTRO 2024

151 patients had some residual hearing prior to SRS, and at last follow-up 35 (23%) (11/57 1# and 26/94 6#) of these patients had lost useful hearing, and 28 (18%) (12/57 1# and17/94 6#) now needed a hearing aid.

37 (13%) had a deterioration in balance (18/102 (1# and 19/182 6#) and 16/102 (6%), but balance actually improved in 16 (6%) of patients (5/102 1# and 11/182 6#).

22 (7%) developed new trigeminal numbness/tingling and 8 (3%) discomfort needing analgesics. All 8 received 6# so likely reflects larger tumour size and consequent trigeminal nerve compression.

16 (5%) patients needed a course of steroids for a deterioration in facial nerve function. Three (3%) received 1# and 13 (7%) had 6#. However, of the 6# patients who developed facial weakness 4 were in an initial cohort of 13 (30%) where the treatment was prescribed to the 80% isodose. Upon identifying increased toxicity compared to prior X knife experience, we reverted to prescribing to the 90% isodose and the rate dropped to expected levels (9/169 = 5%).

Of the 284 patients, 6 (2%) developed new permanent House Brackman ≥3 weakness, none received 1#, two (1%) 30Gy to 90%, and four (30%) 30Gy to 80%.

The median follow-up is 45 months (range 12-141), with median 30 months for 1# patients and 50 months for 6# patients. Nineteen have died; three of complications of VS (1 progression, 1 following a complication of a shunt, and 1 haemorrhage into VS), 7 died of cancer (including 1 GBM). 235 patients had minimum 24-month follow-up and in these 60 (26%) VS was larger on 1st scan and 33 had enlargement on ≥ 2 scans, but of these 13 subsequently reduced to baseline or smaller, 8 stabilised or reduced but remains larger than pre-SRS, and 12 (4%) had progressive enlargement.

Of the 12 with progressive enlargement 3 died of their VS, 3 underwent resection, 3 had shunt or ETV, and 3 continue on surveillance. All were treated with 6#, most likely reflecting larger pre-SRS volume.

Conclusion:

This audit demonstrates evolving practice over time driven by clinical evidence and technological developments. The use of 1# for smaller and 6# for larger VS demonstrates excellent 2-year local control rate of 96% and toxicity similar to other published series 1 .

Keywords: Vestibular schwannoma, radiosurgery, outcomes

References:

1 EANO guideline on the diagnosis and treatment of vestibular schwannoma. Goldbrunner R, Weller M, Regis J, et al. Neuro Oncol. 2020 Jan 11;22(1):31-45