To compare the adverse reaction and cosmetic effect of intraoperative radiotherapy using mobile photon beam with post-operative external radiotherapy as a boost to the tumor bed in patients with early-stage breast cancer receiving breast conserving surgery.

The clinical data of breast cancer patients who underwent breast-conserving surgery from December 2014 to June 2018 were analyzed retrospectively. Patients were divided into intraoperative radiotherapy (72 cases) and post-operative external radiotherapy (150 cases) groups. All patient were treated with radiation therapy to whole breast ± regional nodes at the dose of 50 Gy in 25 fractions. The adverse reaction and cosmetic effect were followed up as well as postoperative recurrence.

Median follow-up period was 35 months (11-52 months). Patients developed less breast fibrosis in intraoperative radiotherapy group compared with post-operative external radiotherapy group (2.8% vs 13.3%, χ²=6.071, P=0.014). However, patients developed more postoperative hematoma in intraoperative radiotherapy group compared with post-operative external radiotherapy group (5.6% vs 0, P=0.015). There is no significant difference between the postoperative infection and necrosis resulted in delayed incision healing and moderate or above breast pain in the irradiation field. The overall incidence of adverse reactions was 13.9% and 16.0% respectively, and the difference was not statistically significant. Patients had excellent or good cosmetic outcome was 83.3% in intraoperative radiotherapy group and 89.3% in post-operative external radiotherapy group. The 3-year local recurrentce rate was 0 in intraoperative radiotherapy group and 1.3% in post-operative external radiotherapy group.

Compared with postoperative external radiotherapy as a boost to the tumor bed, the intraoperative radiotherapy after breast-conserving surgery shows acceptable adverse reaction and similar cosmetic outcome as well as short-term efficacy.