Dosimetry study comparing single-isocenter high-definition dynamic radiosurgery with multiple-isocenter cone-based stereotactic radiosurgery in treating multiple brain metastases

We sought to compare two radiotherapeutic strategies for treating multiple brain metastases (MBM), assessing delivery efficiency, plan quality, and dosimetry of planning target volume (PTV) and normal tissue. Our study population included 21 patients treated for MBM, each reliant on high-definition dynamic radiosurgery (Monaco-HDRS) or cone-based stereotactic radiosurgery (SRS) treatment plans. Monaco-HDRS plans called for one isocenter for all targets. In cone-based plans, each target corresponded with one isocenter. To compare these modalities, we assessed: monitor units (MU); new conformity index (nCI); dose gradient index (GI); homogeneity index (HI); PTV minimum/maximum (Dmax/Dmin) and mean (Dmean) doses; maximum doses to lenses, optic nerves, and brainstem; and brain dose volumes at 3, 6, 10, 12, and 22 Gy (V3Gy-V22Gy). The Monaco-HDRS treatment plan proved more efficient, displaying lower MU, HI, and nCI values and better dosimetry (Dmax/Dmin and Dmean) for PTV. The cone-based plan yielded a lower GI value and dose volumes at 3 Gy and 22 Gy (V3Gy, V22Gy) for brain. There were no significant differences among other parameters. The Monaco-HDRS plan improved treatment efficiency, conformity, and homogeneity, although dose fall-off was worse. The cone-based plan reduced normal brain dose volumes at 3 Gy and 22 Gy.