Hypofractionated stereotactic radiotherapy for large brain metastases: Optimizing the dosimetric parameters

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 (R) non-coplanar multiple dynamic conformal arcs (DCA) HFSRT for >= 25 mm diameter single BM were included. Three other volumetric modulated arc therapy (VMAT) treatment plans were evaluated: with coplanar arcs (Eclipse (R), Varian, VMATc(Eclipse)(R)), with coplanar and non-coplanar arcs (VMATnc(Eclipse)(R)), and with non-coplanar arcs (Elements Cranial SRS (R), Brainlab, VMATnc(Elements)(R)). The marginal dose prescribed for the PTV was 23.1 Gy (isodose 70%) in three fractions. The mean GTV was 27 mm(3). 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 VMATnc(Elements)(R) 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 (V5 Gy) was lower with VMATnc(Eclipse)(R) or VMATnc(Elements)(R) than with DCA (81 or 94 cc vs 110 cc, P=0.02). Conclusions. - NovalisTx (R) VMAT HFSRT for >= 25 mm 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. (C) 2020 Published by Elsevier Masson SAS on behalf of Societe francaise de radiotherapie oncologique (SFRO).

Automated summary

The study aimed to compare dosimetric results of four plans for hypofractionated stereotactic radiotherapy (HFSRT) for large brain metastases, finding that NovalisTx (R) VMAT HFSRT provided the best dosimetric compromise for >= 25 mm diameter brain metastases in terms of target coverage, sparing of healthy brain tissue, and low-dose delivery compared to DCA.