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Purpose Emerging data suggest that higher radiation doses in post-mastectomy radiotherapy may be associated with an increased risk of reconstruction complications. This study aimed to validate previous findings regarding the impact of radiation dose on complications among women with breast cancer using a multi-center dataset. Methods Fifteen institutions participated, and women with breast cancer who received radiotherapy after either autologous or prosthetic breast reconstruction were included. The primary endpoint was major post-radiation therapy complications requiring re-operation for explantation, flap failure, or bleeding control. Results In total, 314 patients were included. Radiotherapy was performed using both conventional fractionation and hypofractionation in various schedules. The range of the radiation therapy dose in Equivalent Dose in 2 Gy fractions (EQD2; α/β = 3.5) varied from 43.4 to 71.0 Gy (median dose: 48.6 Gy). Boost radiation therapy was administered to 49 patients. Major post-radiation therapy complications were observed in 24 (7.6%) patients. In multivariate analysis, an increasing EQD2 per Gy (odds ratio [OR]: 1.58, 95% confidence interval [CI]: 1.26–1.98; p, Highlights • Radiation dose is associated with the risk of breast reconstruction complications. • We conducted a retrospective multi-center observational study of 314 women in Korea. • Complication-related risk factors were identified using multivariate analysis. • Use of hypofractionated radiation therapy may improve breast reconstruction outcomes. • A prospective multi-center study is under way to further validate our findings.

Purpose The details of breast reconstruction and radiation therapy (RT) vary between institutions; therefore, we sought to investigate the practice patterns of radiation oncologists who specialize in breast cancer. Materials and methods We identified the practice patterns and inter-hospital variations from a multi-center cohort of women with breast cancer who underwent post-mastectomy RT (PMRT) to the reconstructed breast at 16 institutions between 2015 and 2016. The institutions were requested to contour the target volume and produce RT plans for one representative case with five different clinical scenarios and answer questionnaires which elicited infrastructural information. We assessed the inter-institutional variations in RT in terms of the target, normal organ delineation, and dose-volume histograms. Results Three hundred fourteen patients were included; 99% of them underwent immediate reconstruction. The most irradiated material was tissue expander (36.9%) followed by transverse rectus abdominis musculocutaneous flap (23.9%) and silicone implant (12.1%). In prosthetic-based reconstruction with tissue expander, most patients received PMRT following partial deflation. Conventional fractionation and hypofractionation RT were used in 66.6% and 33.4% patients, respectively (commonest: 40.05 Gy in 15 fractions [17.5%]). Furthermore, 15.6% of the patients received boost RT and 53.5% were treated with bolus. Overall, 15 physicians responded to the questionnaires and six submitted their contours and RT plans. There was a significant variability in target delineations and RT plans between physicians, and between clinical scenarios. Conclusion Adjuvant RT following post-mastectomy reconstruction has become a common practice in Korea. The details vary significantly between institutions, which highlights an urgent need for standard protocol in this clinical setting.