RapidArc dynamic: A novel volumetric modulated arc therapy technique integrating static and dynamic collimator rotation: A critical appraisal for breast radiotherapy.

RapidArc Dynamic is an advanced evolution of arc-based radiotherapy that extends the principles of VMAT with real-time modulation of gantry speed, dose rate, and dynamic collimator within a single treatment arc. The aim of this study is to investigate how the dynamic collimator rotation and gantry pausing influence treatment quality - results relative to 3DCRT with Field-in-Field (3DCRT-FiF), IMRT, and VMAT planning approaches within the FAST-Forward framework. A retrospective study was conducted on 30 previously treated patients with early-stage breast cancer. Each patient was replanned using four techniques: 3DCRT-FiF, IMRT, VMAT, and RapidArc Dynamic (RAD), generating a total of 120 treatment plans. The prescribed dose was 26.0 Gy in 5 fractions, generated on TrueBeam linear accelerator using Eclipse TPS (v18.1). Treatment Planning was assessed using DVH metrics for PTV and OARs for dose analysis. All techniques achieved acceptable PTV coverage, normalized with V95 % = 95 % of the target volume. 3DCRT-FiF achieved robust coverage but resulted in higher OAR doses. IMRT improved homogeneity but obtained higher monitor units. VMAT offered improved conformity and OARs sparing but demonstrated a larger low-dose bath. RAD achieved the most favorable balance, with superior conformity, reduced OARs doses, minimized low-dose exposure, and reduced treatment delivery time. The mean body dose was observed to be 2.67 Gy, 2.15 Gy, 2.56 Gy, and 2.13 Gy for 3DCRT-FiF, IMRT, VMAT, and RAD, respectively. The total optimization and dose calculation time for RAD were observed to be approximately less than 5.0 min. RapidArc Dynamic approach provides superior dosimetric advantages over conventional techniques for FAST-Forward regimens in breast patients.