Evaluating the Safety and Efficacy of a Novel Accelerated Partial Breast Irradiation Regimen

This study will use an adjuvant radiation therapy regimen called APBI (accelerated partial breast irradiation). APBI is a treatment option available to women considered to have an early stage, low-risk breast cancer. The standard external beam-based APBI treatment delivers treatments every other day for five treatments, over ten calendar days. The APBI in this study is modified and will deliver five once daily treatments over consecutive treatment days, with a slightly lower dose of radiation each day as compared to the standard external beam-based APBI treatment.