Ultra-Hypofractionated Partial Breast Re-Irradiation for Ipsilateral Breast Tumor Recurrence

Background: Salvage mastectomy has traditionally been the standard treatment for ipsilateral breast tumor recurrence (IBTR) following breast-conserving therapy (BCT). Repeat lumpectomy followed by brachytherapy-based or hyperfractionated external beam partial breast re-irradiation (PBrI) has emerged as an alternative in select patients. Ultra-hypofractionated PBrI offers a potentially more convenient approach, but its use remains under investigation. This study evaluates the safety and feasibility of ultra-hypofractionated PBrI following repeat lumpectomy. Methods: Twenty-five consecutively treated women with IBTR after prior BCT including whole-breast irradiation, who underwent repeat lumpectomy followed by ultra-hypofractionated PBrI between 2021 and 2025 were identified from a prospectively maintained, multicenter, single-institution database. Treatment consisted of 26 Gy in five daily fractions using VMAT; two patients received a simultaneous integrated boost to 30 Gy. Acute (<3 months) and chronic (>3 months) side effects (CTCAE v4.0), cosmetic outcome (Harvard scale), IBTR, regional and distant failure, and overall survival were assessed. Kaplan–Meier estimates analyzed time-to-event outcomes. Results: Median age at recurrence was 70 years, with a median interval of 16.6 years from initial treatment. At recurrence, most tumors were stage 0–I (96%), grade 1–2 (88%), ER-positive (92%), HER2-negative, with a median size of 1.2 cm; 56% recurred in the same quadrant. Following PBrI, one patient experienced an IBTR, yielding a crude local control rate of 96%. No regional failure, distant failure, or death occurred. Acute side effects were grade 1 only, including dermatitis (44%), breast edema (12%), breast pain (8%), and fatigue (8%). Late side effects included grade 1/2 breast shrinkage (50%), fibrosis/induration (48%), edema (8%), and telangiectasia (4%). Cosmetic outcome was rated as excellent/good in 71%, and 13% experienced a decline to poor/fair after repeat BCT. Conclusions: Ultra-hypofractionated PBrI following repeat lumpectomy appears to be well tolerated, with acceptable cosmetic outcomes and short-term cancer control in appropriately selected patients. Larger prospective studies are warranted to validate these findings.