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Published on: June 7, 2015
Bilateral breast treatment in a single arc using RapidArc Dynamic: A planning comparison with conventional volumetric
Taoran Li1,2, Luca Cozzi2,3, Lesley Rosa2
1Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Purpose:
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.
Methods:
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 (Dmean, V15Gy), and esophagus (Dmean, D0.03 cm3). Planning time, monitor units (MU), and measured delivery times were also assessed.
Results:
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 cm3 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).
Conclusion:
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.
