A novel weight optimized dynamic conformal arcs with TrueBeam™ Linac for very small tumors (≤1 cc) with single isocenter of multiple brain metastases (2≤, ≥4) in stereotactic radiosurgery: a comparison with volumetric modulated arc therapy

Abstract

Introduction: We evaluated whether improved increase delivery efficiency of weight optimized dynamic conformal arc (WO-DCA) therapy in comparison to volumetric modulated arc therapy (VMAT) with single isocenter for SRS treatment of very small volume and multiple brain metastases (BMs). Materials and Methods: 20 patients having a less than 1 cc volume and 2 <=, >= 4 of multiple BMs, redesigned for 20 Gy in 1 fraction using WO-DCA and VMAT techniques with double full coplanar and three partial noncoplanar arcs. Plan qualities were compared using tumor coverage, conformity index (CI), gradient index (GI), V-4Gy, V-10Gy, and V-12Gy volumes of brain, monitor units (MUs), and percent of quality assurance pass rate (QA%). Results: Both techniques satisfied clinical requirements in coverage and CI. VMAT had a significantly higher MU and mean GI than WO-DCA (for MUs; 2330 vs. 1991; P < 0.001, and for GI; 4.72 vs. 3.39; P < 0.001). WO-DCA was found significantly lower V-4Gy (171.11 vs. 232.80 cm(3), P < 0.001), V-10Gy (25.82 vs. 29.71 cm(3), P < 0.05), and V-12Gy (14.35 vs. 17.28 cm(3), P < 0.05) volumes than VMAT. WO-DCA was associated with markedly increase QA pass rates for all plans (97.65% vs. 92.64%, P < 0.001). Conclusions: WO-DCA may be the first choice compared to the VMAT in reducing the dose in the brain and minimizing small-field dosimetric errors for very small SRS treatment of brain metastases in the range of <= 1 cc and 2 <=, >= 4.