Safety of radiotherapy in patients undergoing breast reconstruction based on patient-reported outcomes: a multicenter collaborative study.

[BACKGROUND] Post-mastectomy radiation therapy (PMRT) improves oncological outcomes of high-risk patients with breast cancer. However, its impact on breast reconstruction remains unclear. This study aimed to evaluate the safety of PMRT in breast reconstruction from the patient's perspective.

[METHODS] This multicenter cross-sectional study was conducted in 10 Japanese institutions. Patient-reported outcomes (PROs) were collected using a comprehensive questionnaire incorporating surgical complications and the Japanese version 2.0 of the BREAST-Q "Adverse effect of radiation" module from 830 patients with breast cancer who had undergone reconstruction (214 with PMRT, 616 without). Complication rates were compared between the PMRT and non-PMRT groups. Logistic regression analysis was used to identify independent predictors of complications.

[RESULTS] The PMRT group showed a significantly higher overall complication rate (76.2% vs. 45.3%, P < 0.001), including dermatitis (48.1% vs. 9.9%, P < 0.001), cutaneous necrosis (9.8% vs. 2.9%, P < 0.001), capsular contracture (16.4% vs. 4.9%, P = 0.020), breast asymmetry (24.3% vs. 17.0%, P = 0.020), and upper limb lymphedema (7.5% vs. 1.1%, P < 0.001) versus the non-PMRT group. In the multivariate analysis, PMRT was identified as an independent risk factor only for cutaneous necrosis (P < 0.001). Adverse effects of radiation were observed in the PMRT group, including dryness (52.3%), pigmentation (46.4%), irritation (39.8%), soreness (38.7%), telangiectasias (36.4%), and skin thickness changes (33.2%).

[CONCLUSION] This is the first large-scale investigation in Japan to evaluate PMRT-related complications in patients who underwent breast reconstruction using PROs. Although PMRT increases complication rates, its direct impact is limited. These findings highlight the importance of incorporating patient-centered data into shared decision-making regarding reconstruction strategies.