Implementing stereotactic accelerated partial breast irradiation using magnetic resonance guided radiation therapy

Highlights: • Prospective dosimetric outcomes for stereotactic MR-guided stereotactic APBI. • In both the 1 and 3 fraction trials, 88.53% of the dosimetric objectives were met. • SBRT-style dosimetry for APBI is feasible using MR-guidance. • Guide for other institutions for clinical implementation of MRg-SAPBI. Accelerated partial breast irradiation (APBI) seeks to reduce irradiated volumes and radiation exposure for patients while maintaining acceptable clinical outcomes. Magnetic resonance image-guided radiotherapy (MRgRT) provides excellent soft-tissue contrast for treatment localization, which can reduce setup uncertainty, thus reducing margins in the external beam setting. Additionally, stereotactic body radiotherapy (SBRT)-style regimens with high gradients can also be executed. This MR-guided stereotactic APBI (MRgS-APBI) approach can be utilized for a lower number of fractions and spare a greater volume of healthy tissues compared to conventional 3D external beam APBI.