Comparison of Planned Versus Actual Dose Delivered for External Beam Accelerated Partial Breast Irradiation Using Cone-Beam CT and Deformable Registration

The current CTV-to-PTV margin of 10 mm appears sufficient for ∼92% of patients treated with EB APBI. Although expansion of the population PTV margin to 14 mm would provide ∼97% confidence level for CTV coverage, online image guidance should be considered.