Central Nervous System

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MO_3_2521 - A Single-Centre Prospective Assessment of Mask Versus Frame Fixation during Gamma Knife Treatment for Brain Metastases

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

A Single-Centre Prospective Assessment of Mask Versus Frame Fixation during Gamma Knife Treatment for Brain Metastases
M. A. Grimm1, U. Koeppen2, F. Stieler1, G. Welzel1, M. Polednik1, F. Wenz1, S. K. Mai1, and F. A. Giordano1; 1Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany, 2University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany

Purpose/Objective(s): The recently introduced stereotactic radiosurgery (SRS) offers traditional frame-based as well as a frameless thermoplastic mask fixation combined with cone beam CT (CBCT)-based image-guidance, automatic positional delivery correction and infra-red based high-definition motion management (HDMM). Here we report outcomes of a prospective non-randomized study on mask fixation (MF) compared to frame fixation (FF) for stereotactic radiosurgery treatment of brain metastases.

Materials/Methods: Between January 2015 and October 2016 we prospectively enrolled patients with brain metastases and indication for primary radiosurgery. The decision FF or MF was made on a case-by- case basis, whereas factors taken into account included patients’ preference, proximity of critical structures, V12 and treatment time. All treatment doses were prescribed to the 50% isodose line. In case of mask fixation a circumferential PTV-margin of 1mm was applied. After treatment, all patients underwent quarterly MRI scans and clinical follow-ups. Primary outcome was local control rate, assessed by RANO criteria and, if required MRI perfusion scans or 18FET-PET-CT. Secondary endpoints were progression free survival (PFS), overall survival (OS) and the incidence of radionecrosis.

Results: 76 patients were enrolled with a total of 197 lesions. 17 patients with 28 lesions received MF and 59 patients with 169 lesions received FF. 187 lesions were treated with stereotactic radiosurgery (SRS) and 10 with fractionated stereotactic radiotherapy (FSRT) (1 lesion with MF and 9 lesions with FF) in up to 3 fractions. The median total dose was 22 Gy in both the MF (range: 16-24 Gy) and FF (range: 10-30 Gy) group. Demographics and histology were balanced. Median follow-up was 9.3 months. There was no significant difference in local failure rate (HR: 0.27; 95% CI: 0.07-1.11; p=0.07) with no local failure occurring in the MF cohort and 11 local failures with FF. No differences were observed between the groups for OS (median: not reached vs. 16.9 months; HR: 1.03; 95% CI: 0.42-2.59; p=0.94) and PFS (median: 6.9 vs. 8.4 months; HR: 1.00; 95% CI: 0.45-2.21; p=0.99). No radionecrosis occurred in the MF cohort compared to 3 cases with FF (p=0.86).

Conclusion: Thermoplastic mask fixation compared to frame fixation during stereotactic radiosurgery treatment for brain metastases does not result in inferior local control, systemic PFS, OS or increased rates of radionecrosis in this non-randomized study with selected patients.

Author Disclosure: M.A. Grimm: None. G. Welzel: None. M. Polednik: None. F. Wenz: None. S.K. Mai: None. F.A. Giordano: None.

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