Hypofractionated Partial Breast Reirradiation in the Conservative Retreatment of Breast Cancer Local Recurrence.

Purpose: To evaluate the outcome of partial breast reirradiation (re-PBI) with intensity modulated radiation therapy using a hypofractionated scheme for breast cancer (BC) local relapse (LR) operated on with repeat breast-conservative surgery.

Methods and materials: Intensity modulated radiation therapy-based re-PBI was performed using either helical or step-and-shoot modality to deliver 37.05 Gy in 13 fractions in 2.5 weeks. Cumulative incidence of second LR, toxicity, disease-free survival (DFS), BC-specific survival, and overall survival were evaluated.

Results: Between May 2012 and May 2021, 70 patients had re-PBI. The median follow-up (FU) was 6.3 years (quartiles 1-3, 4.0-8.1.). The median age at first LR was 62 years. The median primary BC first LR interval was 12.4 years (range, 1.6-26.7 years). Luminal A-like first LR accounted for 41% of the cases, and the median size was 0.8 cm. During FU, 18 (26%) patients showed a subsequent event: 3 second LRs (corresponding to an 8-year cumulative rate of 4%), 3 regional nodal recurrences, 7 distant metastases, and 5 other primary tumors. At 8 years, DFS, BC-specific survival, and overall survival were 76%, 90%, and 90%, respectively. At multivariate analysis, grade 3 and extensive intraductal components were independent predictors for DFS. For 51 and 46 patients, chronic toxicity and cosmesis were evaluated, respectively: 4% had grade 3 fibrosis, and cosmesis was deemed good/excellent in just >60% of the cases.

Conclusions: Re-PBI after repeat breast-conservative surgery represents a feasible alternative to mastectomy with regard to local control, showing an acceptable toxicity profile. A long-term FU is crucial to better understand the pattern of relapse and consolidate the position of re-PBI in clinical practice.