Impact of postmastectomy radiotherapy on health-related quality of life and safety in breast cancer patients undergoing breast reconstruction: A multi-center cross-sectional study (Reborn-02).

574 Background: Postmastectomy radiotherapy (PMRT) is the standard treatment for improving the prognosis of patients with high-risk breast cancer. Expanded indications for breast reconstruction (BR) will likely increase the number of patients undergoing BR who require PMRT, but combining BR with PMRT raises concerns about complications and aesthetics. Evaluating the impact of PMRT on the health-related quality of life (HR-QOL) in Japanese patients is essential for shared decision-making (SDM). This study assessed differences in postoperative HR-QOL and complications between patients who underwent BR with or without PMRT. Methods: We conducted a multicenter cross-sectional study using a questionnaire survey of patients with primary breast cancer who underwent BR between January 2008 and December 2022 at participating institutions, which was approved by the respective institutional review boards. We used the Japanese version of the BREAST-Q questionnaire and questions on patient backgrounds. Results: We included 1078 patients with primary breast cancer. The questionnaire response rate was 77.0% (830/1078). The non-PMRT and PMRT groups comprised 616 and 214 patients, respectively. The PMRT group had higher rates of axillary lymph node dissection (11.7% vs. 52.4%; P<0.001), adjuvant hormonal therapy (67.2% vs. 90.6%; P<0.001), and perioperative chemotherapy (31.8% vs. 84.0%; P<0.001) than the non-PMRT group. Moreover, the overall complication rate (45.3% vs. 76.2%, P<0.001) and the rates of dermatitis (9.9 vs. 48.1%; P < 0.001), skin necrosis (2.9 vs. 9.8%; P<0.001), breast asymmetry (17.0% vs. 24.3%; P=0.002), capsular contracture (4.9 vs. 16.4%; P<0.001), and lymphedema of the upper limb (1.1% vs. 7.5%; P<0.001) were higher in the PMRT group. Multivariate analysis revealed PMRT as an independent risk factor for dermatitis, skin necrosis, and capsular contracture. In the BREAST-Q assessment, the PMRT group showed lower satisfaction with the breast (55 vs. 49; P<0.001), and with physical (85 vs. 76; P<0.001), psychosocial (55 vs. 49; P<0.001), and sexual well-being (36 vs. 34; P=0.021) than the non-PMRT group. Multiple regression analysis revealed PMRT as an independent factor associated with low BREAST-Q scores for breast satisfaction and physical and psychosocial well-being in patients with BR. Conclusions: This is the first large-scale, multi-institutional study to use patient-reported outcomes to assess the effects of PMRT on HR-QOL in Japanese patients with breast cancer who underwent BR. PMRT was associated with an increased risk of complications and decreased HR-QOL in patients with BR. Of note, these findings do not negate the role of PMRT in patients undergoing BR, but highlight the importance of SDM based on realistic HR-QOL expectations after breast reconstruction surgery with PMRT.