Immediate versus DElayed AutoLogous Breast REconstruction and postmaSTectomy radiotherapy (IDEAL BREAST) The IDEAL reconstruction-radiotherapy timing.

Background: Postmastectomy radiotherapy (PMRT) may adversely affect autologous breast reconstruction outcomes. Consequently, immediate breast reconstructions (immediate-BR) are historically discouraged and instead delayed breast reconstructions (delayed-BR) are performed to avoid irradiating flaps. We evaluated complications and long-term patient-reported Health-Related Quality-of-Life (HR-QoL), comparing immediate-BR with delayed-BR in patients with and without PMRT, in two centers where both techniques are being offered, and are based on shared-decision making. Methods: Retrospective and cross-sectional multicenter study. All women undergoing autologous breast reconstruction between 2012-2024 were eligible. Patients were categorized into four groups: immediate-BR and delayed-BR with PMRT, and immediate-BR and delayed-BR without PMRT. Major and minor complications, and patient-reported HR-QoL and satisfaction (BREAST-Q) were analyzed. Results: 1,095 breast reconstructions were included (793 patients): 12.8% irradiated immediate-BR, 15.5% irradiated delayed-BR, 41.6% unirradiated immediate-BR, and 30.1% unirradiated delayed-BR. Major complication rates were comparable between irradiated (immediate-BR 6.4%, delayed-BR 3.5%, p=.29) and unirradiated (immediate-BR 5.1%, delayed-BR 5.8%, p=.75) reconstructions. Similarly, no statistically significant differences were observed for minor complications. On multivariate analysis, current smoking was an independent risk factor for complications in unirradiated patients, while harvesting multiple perforators was associated with a reduced risk. The median BREAST-Q follow-up was 5.0 years. Among irradiated patients, immediate-BR and delayed-BR yielded comparable HR-QoL with no statistically significant difference across any domain. Conclusion: Complication rates and long-term HR-QoL were comparable in patients undergoing immediate-BR and delayed-BR requiring PMRT. Therefore, immediate-BR should be considered viable for women considering autologous reconstruction with PMRT.