Purpose: Stereotactic radiotherapy plays a major role in the treatment of brain metastases (BM). We aimed to compare the dosimetric results of four plans for hypofractionated stereotactic radiotherapy (HFSRT) for large brain metastases.
Material and methods: Ten patients treated with upfront NovalisTx® non-coplanar multiple dynamic conformal arcs (DCA) HFSRT for≥25mm diameter single BM were included. Three other volumetric modulated arc therapy (VMAT) treatment plans were evaluated: with coplanar arcs (Eclipse®, Varian, VMATcEclipse®), with coplanar and non-coplanar arcs (VMATncEclipse®), and with non-coplanar arcs (Elements Cranial SRS®, Brainlab, VMATncElements®). The marginal dose prescribed for the PTV was 23.1Gy (isodose 70%) in three fractions. The mean GTV was 27mm3.
Results: Better conformity indices were found with all VMAT techniques compared to DCA (1.05 vs 1.28, P<0.05). Better gradient indices were found with VMATncElements® and DCA (2.43 vs 3.02, P<0.001). High-dose delivery in healthy brain was lower with all VMAT techniques compared to DCA (5.6 to 6.3 cc vs 9.4 cc, P<0.001). Low-dose delivery (V5Gy) was lower with VMATncEclipse® or VMATncElements® than with DCA (81 or 94 cc vs 110 cc, P=0.02).
Conclusions: NovalisTx® VMAT HFSRT for≥25mm diameter brain metastases provides the best dosimetric compromise in terms of target coverage, sparing of healthy brain tissue and low-dose delivery compared to DCA.
Keywords: Brain metastasis; Dosimetry; Dosimétrie; Métastases cérébrales; NovalisTx®; RCMI; Radiothérapie stéréotaxique; Stereotactic radiotherapy; VMAT.
Copyright © 2020. Published by Elsevier Masson SAS.