WBRT applied after IORT is associated with increased risk of seroma evacuation, which might be considered as a late side effect.

Introduction: Intraoperative radiotherapy (IORT) based on low-kV photons may be an option for early breast cancer patients. Following Targit trial results some of those patients should undergo whole breast irradiation (WBRT) additionally. Material and methods:Since April 2010, IORT has been applied to early breast cancer patients. One hundred and fifty patients were prospectively followed up and examined to evaluate the side effects (pain, fibrosis, breast edema, telangiectasias). We present the results 3 years post-treatment. WBRT was given to 82 (54.7%) patients. Results:Tumor cavity fibrosis grade II and more was observed in 18 (12%) patients, as grade III only in 2 (1.33%) patients. Breast tissue fibrosis outside tumor cavity grade II was observed only in 2 (1.33%) patients. Breast edema was present in 10 (6.66%) patients. WBRT administration led to increased frequency of higher grade tumor cavity fibrosis (P < .0001), breast fibrosis (P < .0001), breast edema (P = .003), and occurrence of telangiectasias (P = .03), with no influence on pain reported by patients.In case of WBRT, tumor location (P = .026) and size of the irradiated breast (P = .015) were independent risk factors for higher degree of breast fibrosis, as seroma evacuation 6 months post-WBRT (P = .036) was the only independent risk factor for higher level of tumor cavity fibrosis in multiple regression. Conclusions:The cosmetic result after IORT is good and comparable to other accelerated partial breast irradiation techniques. Administration of WBRT post-IORT in breast cancer patients increases the level of fibrotic changes, breast edema and telangiectasias 3 years post-treatment, but with no influence on pain. K E Y W O R D Sbreast cancer, breast edema, fibrosis, intraoperative radiotherapy, pain, side effects, telangiectasias, whole breast radiotherapy

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.