High Five (HiFi) Accelerated Partial Breast Irradiation Study

To establish the role of adjuvant multicatheter interstitial high-dose-rate brachytherapy in doubly accelerated and radiobiologically equivalent irradiation scheme of 5 x 5,4 Gy in 3 days of treatment (High Five, HiFi-APBI) compared to the adopted long-term standard of APBI realized in 4-5 days (7-8 x 4-4,3 Gy) in selected women with breast low-risk invasive cancer or carcinoma in-situ, in terms of 3-month early and 2-year late toxicity.