Treatment of Multiple Brain Metastases Using Stereotactic Radiosurgery with Single-Isocenter Volumetric Modulated Arc Therapy: Comparison with Conventional Dynamic Conformal Arc and Static Beam Stereotactic Radiosurgery

Both dynamic conformal arc therapy (DCAT) and three-dimensional conformal radiation therapy (3D-CRT) are well-established techniques and have commonly been used for stereotactic radiosurgery (SRS) treatment in brain metastases. However, for multiple metastases, a much longer treatment time results from multi-isocenter setup in DCAT and 3D-CRT. The aim of this study is to investigate the treatment of multiple brain metastases using single-isocenter volumetric modulated arc therapy (VMAT) compared with conventional multi-isocenter DCAT and 3D-CRT.;A series of 17 patients with 2 to 5 brain metastatic lesions were studied. For patients treated with DCAT/3D-CRT plans, VMAT plans were retrospectively generated, and vice versa. The number of isocenters was proportional to the number of PTVs in DCAT/3D-CRT plans while single-isocenter was employed in VMAT plans. The DCAT/3D-CRT and VMAT plans were generated using BrainLAB iPlan RTM RT Dose v4.1.1 and Varian Eclipse(TM) v8.6 treatment planning system, respectively. All plans were designed to be delivered on Novalis Tx(TM) system.;Conformity for VMAT plans was equivalent to or better than that for DCAT/3D-CRT plans. VMAT and DCAT/3D-CRT plans have similar target coverage, and VMAT plans have higher quality of coverage. However, the mean increase of 46% in the volume of low-dose region receiving 5 Gy was observed in VMAT plans. In addition, the distance between individual PTVs and VMAT isocenter has no impact on VMAT plans. The mean monitor units (MU) decreased by 42% and the mean treatment time decreased by 49% for VMAT plans.;This work suggests that single-isocenter VMAT is promising for SRS in the treatment of multiple brain metastases. Single-isocenter VMAT is able to achieve comparable dose conformity, target coverage, and quality of coverage to conventional DCAT and 3D-CRT plans with significantly superior delivery efficiency. However, single-isocenter VMAT might result in a larger low-dose region.