For early stage breast cancer patients who have received whole breast radiotherapy as part of their initial treatment, and then present with ipsilateral breast recurrence, a standard treatment option is mastectomy. Recent reports indicate that well-selected patients can be treated with a second breast conserving surgery and partial breast reirradiation with good toxicity and clinical outcomes. We report the patient characteristics and clinical outcomes for patients treated with a second breast conserving treatment with intraoperative radiotherapy (IORT) at our institution. Materials/Methods: Records were retrospectively reviewed of 61 locally recurrent breast cancer patients treated with IORT in the setting of a second breast conserving treatment from 2012-2017. All patients had refused mastectomy and elected for a second breast conserving treatment. Results: The median age at time of IORT was 71 years old (range: 44 e 85). The median time interval between the initial surgery and the second surgery was 15.8 years (2.3 e 30.3). The median tumor size was 0.7 cm (0.05 e 2.7). The histologies of the recurrent tumors were 55.7% invasive ductal carcinoma, 18.0% invasive lobular carcinoma, and 24.6% ductal carcinoma in situ. Regarding receptor status, 55/61 (90.2%) were ER or PR positive, 8/61 (13.1%) were Her2+, and 2/61 (3.3%) were triple-negative. Regarding histologic grade, 4/57 (7.0%) were low-grade, 29/57 (50.9%) were intermediate-grade, and 24/57 (42.1%) were high-grade. There was node positivity in 5/61 (8.2%) patients. At a median follow-up time of 10.3 months (0.0 e 51.7), there were 2 distant recurrences (2/61 Z 3.3%) and 3 local recurrences (3/61 Z 4.9%). The two patients with distant recurrence were both diagnosed with bone metastases within a few months of the second breast conserving treatment; both were node-positive. The three local recurrences occurred at 24, 16, and 21 months after the second breast conserving treatment. Two underwent subsequent bilateral mastectomies and the third underwent a third lumpectomy; all three are currently without evidence of disease. Conclusion: For carefully selected patients with locally recurrent breast cancer, IORTas part of a second breast conserving treatment appeared to show acceptable short term clinical outcomes. Nodal status may be a risk factor for a second recurrence. Longer follow-up and proper risk stratification will be necessary to demonstrate efficacy as an alternative treatment option.

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