High Five (HiFi) Accelerated Partial Breast Irradiation Study

All recruited participants will be treated with adjuvant to breast-conserving surgery accelerated partial breast irradiation with multicatheter interstitial brachytherapy technique and prescribed five times 5,4 Gy delivered in 3 consecutive days (6 hours minimum gap between the fractions). Treatment starts not later than 12 weeks after surgery (optimally 4-8 weeks), after wound healing, and obtaining the final pathological report with full immunohistochemistry and proper risk group assignment.