Synchronous bilateral breast cancer (SBBC) presents significant radiotherapy planning challenges due to complex target volumes near critical organs. This study evaluated RapidArc Dynamic (RAD), a novel technique integrating dynamic arcs with static angle modulated ports (STAMPs) via simultaneous GPU-accelerated optimization, against conventional volumetric modulated arc therapy (VMAT) for SBBC treatment planning and delivery efficiency.

Ten retrospective SBBC cases involving comprehensive nodal irradiation were planned using both multi-arc VMAT (six arcs) and RAD (one arc plus six STAMPs) in Eclipse (v18.1) with AcurosXB. A prescription dose of 40.05 Gy in 15 fractions was normalized to PTV D95% = 95%. Paired Wilcoxon signed-rank tests compared planning target volume (PTV) coverage (V95%, V105%) and organ-at-risk (OAR) doses, including lungs (V5Gy, V10Gy, V20Gy), heart (D, V15Gy), and esophagus (D, D0.03 cm). Planning time, monitor units (MU), and measured delivery times were also assessed.

RAD plans achieved clinical goals more frequently than VMAT plans (90% vs. 70% of endpoints). PTV V95% coverage was comparable between the two techniques. However, RAD significantly improved breast dose homogeneity (lower median PTVp V105%; p < 0.05) and OAR sparing. Notably, RAD reduced median lung V5Gy by 9.7% (p < 0.001) and esophageal D0.03 cm by 5.4 Gy (p = 0.002). RAD significantly reduced planning time (avg 16 vs. 39 min), mean MU (1654 vs. 2268; ∼30% reduction), and mean measured delivery time (2.2 vs. 5.8 min; ∼62% reduction).

For SBBC radiotherapy, RAD demonstrated significant dosimetric improvements over conventional VMAT, particularly reducing low-dose lung and high-dose esophageal irradiation while enhancing target homogeneity. The substantial gains in planning and delivery efficiency further establish RAD as a highly advantageous technique for managing these complex cases.