Comparison of Advanced Dynamic Arc Therapy With Collimator Rotation and Fixed Integrated Gantry Positions to the Standard of Care Across Five Treatment Sites

Aim To evaluate dosimetric plan quality, optimization efficiency, and delivery time of RapidArc Dynamic (RAD), a novel treatment planning approach combining dynamic gantry positions with dynamic collimator rotation and user-selected static angle modulated ports (STAMPs), compared to conventional volumetric modulated arc therapy (VMAT) across five anatomical treatment sites. Methods Treatment plans were developed for breast, lung, pancreas/liver, prostate, and head and neck cases. VMAT plans were first optimized following clinical guidelines and dosimetric scorecards. The same optimization objectives from the VMAT plans were applied to the RAD plans. RAD-specific variables, including STAMP selection and weighting, were systematically explored. When the best settings for RAD were found, optimization objectives were modified to further improve quality specific to each case. For equal comparison between the two techniques, the optimization objectives from the RAD plans were copied back to the VMAT plans for re-optimization. Optimization time, monitor units, number of control points, delivery time, and dosimetric plan quality were then compared. Results RAD demonstrated reduced optimization times compared to VMAT, averaging one minute and 23 seconds versus two minutes and seven seconds. Dosimetric improvements were observed across all sites: breast plans showed reduced heart mean dose (1.98 vs. 1.23 Gy) and improved dose homogeneity; lung plans achieved better heart V5Gy; prostate plans demonstrated enhanced bladder and rectum sparing at V18Gy; and head and neck plans showed improved sparing of the lips and oral cavity. Treatment delivery times were reduced in most cases, with improvements ranging from 11% to 25% in breast, lung, and head and neck. Conclusions RAD offers faster optimization times while maintaining or improving plan quality compared to VMAT. The integration of dynamic collimator rotation and strategic STAMPs can provide enhanced organ-at-risk sparing without compromising target coverage. These improvements, combined with generally reduced delivery times, suggest RAD offers a potential advancement in radiation therapy planning efficiency and plan quality.