ESTRO 2024 - Abstract Book

S947

Clinical - CNS

ESTRO 2024

the cerebellopontine angle was observed in n=12 cases (Koos Gr. II (1), III (3), IV (8)). The mean GTV was 12,6 cm³ (range 0,4-63,9 cm³). For PTV uniformly 3mm margin was added to GTV which resulted in a mean PTV volume of 23,2 cm³ (range 1,5-91,7 cm³).

Results:

The median follow-up time was 24 months (range 3-63 months). 1 patient died due to non-tumor and non treatment related sequela. The 2-years local control is 100%. 14/22 patient had stable disease and 8/22 patient showed partial response at the time of the last follow-up. Tumor regression kinetics show mean tumor regression at 36 months post-FPRT up to 32% (range 2-52%) respectively. 6/9 patients with vestibular schwannoma had serviceable hearing, Gardner-Robertson Score (GRS) 1-2 prior to FPRT. 2 patients experienced worsening of hearing at 6 months follow-up but it stayed stable in the further follow-up (Table 1). The function of the facial nerve by the n=5 patients with schwannoma of the facial nerve was evaluated according to the House-Brackman Grading System [3]. N=2 patients experienced improvement of the facial nerve function, by the remaining n=3 patients the facial function stayed stable during the follow-up (Table 2). In 1 case we observed a grade 3 central nervous system necrosis (CTCAE 5.0) at 6 months which improved to grade 1 at 3-years follow up due to supportive therapy and treatment with dexamethasone and bevacizumab. No other ≥ grade 2 late side effects were observed.

Pat. number

Prior to FPRT 6mo FU

1y FU

2y FU

3y FU

1. 2. 3. 4. 5. 6. 7. 8. 9.

GR 4 GR 2 GR 1 GR 2 GR 1 GR 1 GR 1 GR 3 GR 3

stable stable

stable

stable

stable

GR 2 GR 3

stable stable stable stable stable stable

stable stable stable

stable stable stable

stable stable stable stable stable

stable

stable

Table 1.: Evaluation of hearing according to the Gardner-Robertson classification by the n=9 patients with vestibular schwannoma prior to FPRT and during the follow-up

Pat. number

Prior to FPRT 6mo FU

1y FU

2y FU

3y FU

1. 2. 3. 4. 5.

Grade 1 Grade 2 Grade 5 Grade 1 Grade 2

stable stable

stable

stable stable stable stable

Grade 1

Grade 3

stable stable

stable stable

stable

Table 2.: Evaluation of facial nerve function according to House-Brackmann classification by the n=5 patients with schwannoma of the facial nerve prior to FPRT and during follow-up.

Conclusion: