Clinical implementation of AXB from AAA for breast: Plan quality and subvolume analysis

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Varian Eclipse software offers two dose calculation algorithms: Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB).
• AXB is increasingly available, necessitating an understanding of its impact on radiotherapy planning before clinical adoption.

Purpose of the Study:

• To characterize differences in breast radiotherapy plan quality between AXB and AAA.
• To provide data for clinicians implementing AXB in Varian Eclipse systems.

Main Methods:

• Locoregional breast radiotherapy plans were recalculated using AXB (dose-to-water and dose-to-medium) after initial creation with AAA.
• Target coverage and organ-at-risk doses were compared using dose-volume parameters.
• A subvolume analysis assessed spatial dose distribution differences.

Main Results:

• Median differences in breast clinical target volume (CTV) V95% between AXB and AAA were <2.5%.
• Internal mammary chain (IMC) CTV coverage showed minimal differences (<5% for V95%, 0% for V80%).
• Superficial dose increased by a median of 3.2 Gy, with medial subvolumes hotter and lateral subvolumes cooler by <2 Gy with AXB.

Conclusions:

• AXB and AAA algorithms demonstrate minimal differences in dose magnitude and spatial distribution for breast radiotherapy.
• The largest dose variations were observed in superficial regions.
• Clinical implementation of AXB is not anticipated to necessitate changes in breast radiotherapy prescribing or planning practices.