Significant correlation between gross tumor volume (GTV) D98% and local control in multifraction stereotactic radiotherapy (MF-SRT) for unresected brain metastases

• Published in: Radiotherapy and oncology Vol. 154; pp. 260 - 268
• Main Authors: Dupic, Guillaume, Brun, Lucie, Molnar, Ioana, Leyrat, Brice, Chassin, Vincent, Moreau, Juliette, Dedieu, Véronique, Khalil, Toufic, Verrelle, Pierre, Lapeyre, Michel, Biau, Julian
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.01.2021; Elsevier
• Subjects: Brain metastases; Brain Neoplasms - radiotherapy; Cancer; GTV D98; Humans; Life Sciences; Local control; Radiosurgery; Radiotherapy Dosage; Radiotherapy, Intensity-Modulated; Retrospective Studies; Stereotactic radiotherapy; Tumor Burden; VMAT; HI; OAR; RPA; VMAT; BBB; PS; CTV; MRI; GTV; DS-GPA; Brain metastases; EGFR; Gy; PTV; SRT; SRS; CBV; TPS; MF; PFS; BED; GI; DCA; OS; WBRT; Local control; CI; VEGF; NCI-CTCAE; GTV D98; TKI; LC; GPA; RN; SIR; RP; Stereotactic radiotherapy; ICRU
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2020.11.021

•Monocentric study on brain multifraction SRT using the ICRU 91 reporting standards.•Explicit reporting of PTV and GTV Dmin, D98%, D50%, D2%, Dmax, Dmin, conformity index, gradient index, brain GTV VxGy.•Report GTV D98% as a strong reproducible significant predictive factor of local control.•Dose prescription should lead to a GTV BED12 98% ≥ 52.4–53.4 Gy.•Dose prescription should lead to a GTV D98% ≥ 19.7–20 Gy/1f and 29–29.4 Gy/3f. 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. 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. 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. 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.