Session Item

Stereotactic radiotherapy (SRT) is routinely used to treat Vestibular Schwannomas (VS) to avoid the need for surgical intervention.  It is generally recommended that VS causing brainstem compression are surgically treated.  However, there are some patients who decline surgery or are deemed medically unfit who undergo treatment with SRT.  There is debate amongst clinicians about the best way to treat these large VS and practice varies between 12Gy in 1#, 18Gy in 3# or more prolonged fractionation.

All patients undergoing CyberKnife Radiotherapy for VS at a regional centre were identified from a prospective database. Treated lesions over 4cc with at least 2 years of follow up were included for this analysis.  All patients were given a key worker contact number to report toxicity events and records from outpatient visits were used to establish toxicity data.  Toxicity was documented for facial and trigeminal nerve via CTCAE v4 grading and timing of occurrence and interventions required to manage symptoms were recorded.  Any other acute or late G3 or 4 toxicity was also recorded.

48 patients were included for analysis treated between 07/2013 and 08/2019.  Treatment volume varied from 4.05-11.61cc (mean 5.66cc).  19 (40%) lesions were treated with 3# and 29 (60%) lesions were treated with 1#. The mean size in the 3 vs. 1# groups was 6.44cc (range 4.06cc-11.61cc) vs. 5.15cc (range 4.05cc-6.67cc) (p=0.0025).In total 7 (15%) patient patients experienced any grade acute facial nerve toxicity, 5 (17%) received 1# with 2 (11%) receiving 3# (p=0.52).  6 of the 7 patients experienced G1 facial twitching alone, 1 patient’s facial nerve function deteriorated to House Brackmann G3 toxicity at 5 months and unfortunately long-term follow up of that patient was not achieved as they died of other causes at 15 months post treatment, they had received 1# treatment. 13 patients experienced any grade acute trigeminal nerve toxicity, 9 (31%) receiving 1# treatment with 4 (21%) receiving 3# (p=0.45).  5 patients had persistent symptoms beyond a year and received medical therapy for management, 3 in the 3# group and 2 in the 1# group.  No patients developed hydrocephalus following SRT.

Despite statistically significantly bigger tumour volumes receiving 3# there were lower rates of acute trigeminal and facial nerve toxicity seen in this series although this did not reach statistical significance.  A randomised trial comparing treatment with 12Gy in 1# vs 18Gy in 3# in VS over 4cc not suitable for surgery or where surgery is declined is warranted.