Moderately hypofractionated partial breast reirradiation: early clinical results and dosimetric considerations in the context of 2

Background: Patients submitted to breast conservative surgery (BCS) with whole breast irradiation at the initial disease that experience an isolated ipsilateral breast tumor recurrence, face mastectomy, as the standard treatment. Selected cases may derive good outcomes from repeat BCS and irradiation with partial breast irradiation (PBI) which limits the volume of tissue reducing the risk of increased toxicity. We report our experience with external PBI for locally recurrent breast cancer. Materials and methods: We queried our department's re-RT database for breast cancer treated with external beam radiation therapy (EBRT) from 2017-2021. We reviewed the electronic record for each case with PBI. Demographic, disease characteristics, primary RT/re-RT details and toxicity were collected. Local recurrence-free survival (LR-FS), distant recurrence-free survival (DR-FS) and overall survival (OS) were estimated using the Kaplan-Meier method. Results: Eleven women were reviewed. Mean (standard deviation; SD) age was 54 (38-76) years and Eastern Cooperative Oncology Group (ECOG) Performance Status was 0-1 (100%) with median follow-up from recurrence of 41 months (27-62 months). All presented T1-2 recurrent lesions. Tumors were clinically node negative and no patients had evidence of metastatic disease before undergoing BCS. For the re-RT course, all received PBI with 40 Gy/2,67 Gy daily. Cosmesis results were good. Eight experienced grade 1 erythema and 2 grade 1 pigmentation with 1 pruritus. Major late effects were fibrosis. There were no grade 3 or higher late reactions. At 3 years, 9 patients remained free from LR, 10 from DR, and 9 were alive. Conclusion: In our cohort, a second BCS followed by re-RT with hypofractionation EBRT showed acceptable toxicity and early promising results, though longer follow-up is needed.