Accelerated Partial Breast Irradiation with Intraoperative Radiotherapy Is Effective in Luminal Breast Cancer Patients Aged 60 Years and Older.

Adjuvant whole breast irradiation (AWBI) improves local control and survival in breast cancer patients after breast-conserving surgery. Between 2010 and 2017, 823 patients ≥ 60 years with ER-positive, Her-2 negative, clinically N0 breast cancer underwent breast-conserving surgery (BCS) at the West Pomeranian Oncology Center. Intraoperative radiotherapy (IORT) with kV photons was applied to 199 (24.2%) patients according to the IORT protocol, and AWBI only was applied to 624 (75.8%). IORT patients in cases with lymph node metastasis, lobular type presence, extensive in situ components, lymphatic vessel invasion, or resection margin < 2 mm, additionally underwent AWBI. Median follow-up was 74 months. There were two (1%) breast relapses in the IORT protocol group and one (0.2%) in the AWBI-only group. In each group, one axillary lymph node relapse was diagnosed (0.5% and 0.2%, respectively). There were two local relapses in the IORT-only group, and they were treated further with BCS and AWBI. Although locoregional relapse-free survival differed between the AWBI-only and IORT protocol groups (98.5% vs. 99.7%, p = 0.048), the local control, distant metastasis-free survival, and breast cancer-specific survival were similar. IORT is a reasonable option to avoid AWBI in ER-positive, Her-2 negative, cN0 women with breast cancer aged ≥ 60 years.