Repeat Breast Conserving Surgery Followed by Daily Partial Breast Irradiation for Participants With Ipsilateral Breast Tumor Recurrence Treated Initially With Breast Conserving Surgery and Whole Breast Radiation Therapy

Breast cancer survival rates have greatly improved with advances in both screening and treatment. The standard of care for both early stage and selected locally advanced breast cancers is breast conserving therapy (BCT), consisting of a partial mastectomy followed by radiation treatment. Traditionally, a salvage mastectomy was the standard treatment for women who initially underwent BCT and experienced an ipsilateral breast tumor recurrence (IBTR). Many participants have become increasingly motivated to avoid mastectomy, and there has been rising interest in repeat BCS (Breast Conserving Surgery) with focal radiation for certain participants motivated to keep their breast. The current standard of care for breast re-irradiation after an in-breast tumor recurrence is partial breast irradiation consisting of a dose of 45 Gy delivered BID for 30 fractions. While this regimen demonstrated excellent local control and low AEs, the regimen itself is difficult for participants. Receiving RT twice daily at smaller doses per fraction (1.5 Gy) for 30 treatments can be burdensome, especially for those without reliable transportation or difficulty getting time away from work. Given the excellent local control rates and low rate of AEs, in this study, we hypothesize that daily hypofractionated EBRT(External Beam Radiation Therapy) for re-irradiation after repeat BCS would be at least as well tolerated with good local control and provide a more convenient option for participants than the current standard of care established by RTOG 1014. Some participants will present with high-risk features (e.g. age <50, high grade, ER negative tumors, close margins) making dose escalation an attractive option to improve local control. Options for dose escalation include sequential and concurrent administration of a boost.