Guillaume Dupic1, Lucie Brun2, Ioana Molnar3, Brice Leyrat2, Vincent Chassin4, Juliette Moreau2, Véronique Dedieu4, Toufic Khalil5, Pierre Verrelle2, Michel Lapeyre2, Julian Biau2. 1. Department of Radiation Oncology, Jean Perrin Center, Clermont-Ferrand, France. Electronic address: guillaume.dupic@amethyst.fr. 2. Department of Radiation Oncology, Jean Perrin Center, Clermont-Ferrand, France. 3. Department of Clinical Research UMR 501, Jean Perrin Center, Clermont-Ferrand, France; INSERM U1240 IMoST, University of Clermont Auvergne, Clermont-Ferrand, France. Electronic address: iona.molnar@clermont.unicancer.fr. 4. Department of Medical Physics, Jean Perrin Center, Clermont-Ferrand, France. 5. Department of Neurosurgery, Clermont-Ferrand Hospital, University of Clermont Auvergne, France.
Abstract
BACKGROUND: Stereotactic radiotherapy (SRT) should be applied with a biologically effective dose with an α/β of 12 (BED12) ≥ 40 Gy to reach a 1-year local control (LC) ≥ 70%. The aims of this retrospective study were to report a series of 81 unresected large brain metastases treated with Linac-based multifraction SRT according to the ICRU 91 and to identify predictive factors associated with LC. METHODS: Included in this study were the first 81 brain metastases (BM) consecutively treated with Linac-based volumetric modulated arc therapy (VMAT) multifraction SRT from 2017 to 2019. The prescribed dose was 33 Gy for the GTV and 23.1 Gy (70% isodose line) for the PTV in 3 fractions (3f). Mean BM largest diameter and GTV were 25.1 mm and 7.2 cc respectively. Mean follow-up was 10.2 months. RESULTS: LC was 79.7% and 69.7% at 1 and 2 years respectively. Significant predictive factors of LC were GTV D98% (HR = 0.84, CI 95% = 0.75-0.95, p = 0.004) and adenocarcinoma as the histological type (HR = 0.29, CI 95% = 0.09-0.96, p = 0.042) in univariate and multivariate analysis. A threshold of 29 Gy for GTV D98% was significantly correlated to LC (1-year LC = 91.9% for GTV D98% ≥ 29 Gy vs 69.6% for GTV D98% < 29 Gy (p = 0.030)), corresponding to a BED12 = 52.4 Gy. No tumor progression was observed for a BED12 ≥ 53.4 Gy, corresponding to a GTV D98% ≥ 20 Gy /1f and GTV D98% ≥ 29.4 Gy 3f. Median OS was 15 months. Symptomatic radionecrosis occurred in 4.9% of cases. CONCLUSION: The GTV D98% is a strong reproducible significant predictive factor of LC for brain SRT. Dose prescription should lead to a GTV BED12 98% ≥ 52.4-53.4 Gy to significantly improve LC, corresponding to respectively a GTV D98% ≥ 19.7-20 Gy/1f and 29-29.4 Gy/3f.
BACKGROUND: Stereotactic radiotherapy (SRT) should be applied with a biologically effective dose with an α/β of 12 (BED12) ≥ 40 Gy to reach a 1-year local control (LC) ≥ 70%. The aims of this retrospective study were to report a series of 81 unresected large brain metastases treated with Linac-based multifraction SRT according to the ICRU 91 and to identify predictive factors associated with LC. METHODS: Included in this study were the first 81 brain metastases (BM) consecutively treated with Linac-based volumetric modulated arc therapy (VMAT) multifraction SRT from 2017 to 2019. The prescribed dose was 33 Gy for the GTV and 23.1 Gy (70% isodose line) for the PTV in 3 fractions (3f). Mean BM largest diameter and GTV were 25.1 mm and 7.2 cc respectively. Mean follow-up was 10.2 months. RESULTS: LC was 79.7% and 69.7% at 1 and 2 years respectively. Significant predictive factors of LC were GTV D98% (HR = 0.84, CI 95% = 0.75-0.95, p = 0.004) and adenocarcinoma as the histological type (HR = 0.29, CI 95% = 0.09-0.96, p = 0.042) in univariate and multivariate analysis. A threshold of 29 Gy for GTV D98% was significantly correlated to LC (1-year LC = 91.9% for GTV D98% ≥ 29 Gy vs 69.6% for GTV D98% < 29 Gy (p = 0.030)), corresponding to a BED12 = 52.4 Gy. No tumor progression was observed for a BED12 ≥ 53.4 Gy, corresponding to a GTV D98% ≥ 20 Gy /1f and GTV D98% ≥ 29.4 Gy 3f. Median OS was 15 months. Symptomatic radionecrosis occurred in 4.9% of cases. CONCLUSION: The GTV D98% is a strong reproducible significant predictive factor of LC for brain SRT. Dose prescription should lead to a GTV BED12 98% ≥ 52.4-53.4 Gy to significantly improve LC, corresponding to respectively a GTV D98% ≥ 19.7-20 Gy/1f and 29-29.4 Gy/3f.
Authors: Taoran Cui; Joseph Weiner; Shabbar Danish; Anupama Chundury; Nisha Ohri; Ning Yue; Xiao Wang; Ke Nie Journal: Front Oncol Date: 2022-06-30 Impact factor: 5.738