Local Failure After Accelerated Partial Breast Irradiation with Intraoperative Radiotherapy with Electrons: An Insight into Management and Outcome from an Italian Multicentric Study.

BACKGROUND: The aim of this work is to evaluate pattern of care and clinical outcome in a large series of patients with in-breast recurrence (IBR), after quadrantectomy and intraoperative radiation therapy with electrons (IOERT) as partial breast irradiation. PATIENTS AND METHODS: Patients with IBR after IOERT, treated with salvage surgery ± adjuvant reirradiation (re-RT), were selected from a multiinstitution database. Disease-free survival (DFS), overall survival (OS), cumulative incidence of second IBR, and distant metastases (DM) were estimated. RESULTS: A total of 224/267 patients from seven institutions were included. Primary tumors received 21 Gy. Median time to first IBR was 4.3 years (range 2.6-6.1 years). Salvage mastectomy and repeat quadrantectomy were performed in 135 (60.3%) and 89 (39.7%) patients, followed by adjuvant re-RT in 21/135 (15.5%) and 63/89 (70.8%), respectively. Median follow-up after salvage treatment was 4.1 years. Overall, 5- and 8-year outcomes were as follows: cumulative incidence of second IBR: 8.4% and 14.8%; cumulative incidence of DM: 17.1% and 22.5%; DFS: 67.4% and 52.5%; OS: 89.3% and 74.7%. The risk of second IBR was similar in the salvage mastectomy and repeat quadrantectomy + RT groups [hazard ratio (HR) 1.41, p = 0.566], while salvage mastectomy patients had greater risk of DM (HR 3.15, p = 0.019), as well as poorer DFS (HR 2.13, p = 0.016) and a trend towards worse OS (HR 3.27, p = 0.059). Patients who underwent repeat quadrantectomy alone had worse outcomes (second IBR, HR 5.63, p = 0.006; DFS, HR 3.21, p = 0.003; OS, HR 4.38, p = 0.044) than those adding re-RT. CONCLUSIONS: Repeat quadrantectomy + RT represents an effective salvage approach and achieved local control comparable to that of salvage mastectomy.