Dosimetric and Clinical Factors Associated With Increased Risk of Reconstruction Complications in Patients With Breast Cancer Receiving Post-Mastectomy Radiation

Abstract

Approximately 30% of women who receive post-mastectomy radiation therapy (PMRT) in the setting of breast reconstruction suffer from reconstruction complications. This study aims to assess clinical and dosimetric factors associated with the risk of reconstruction complications after PMRT, with the ultimate goal of identifying a dosimetric constraint that can be utilized clinically to limit this risk.We retrospectively identified 41 patients who underwent modified radical (MRM) or nipple or skin-sparing mastectomy followed by immediate or delayed reconstruction (autologous or implant-based) and radiation at a single institution from 2015-2020. Reconstruction complications were defined as flap or implant failure, necrosis, capsular contracture, cellulitis/infection, implant rupture, implant malposition, leakage/rupture, unplanned operation or hospitalization, and hematoma/seroma. Clinical and dosimetric variables (such as dose heterogeneity measured by V105) associated with complications were assessed with uni- and multivariate analyses using Fischer exact, logistic regression, and 1-sided Wilcoxon rank sum tests.The mean age was 50 years, mean BMI 28.1 kg/m^2, 20% of patients had diabetes mellitus, and 29% had significant smoking history. 18 patients underwent MRM and 23 nipple or skin-sparing mastectomy. 11 patients received autologous reconstruction while 30 patients received an implant. 12 patients underwent delayed reconstruction while 29 patients underwent immediate reconstruction. 39 patients were treated using 3D-CRT and 2 using VMAT. Median prescribed dose was 50 Gy in 25 fractions, 14 patients received a radiation boost (range 8-16 Gy), and 26 were treated with bolus. Twelve patients (29%) suffered from reconstructioncomplications (6 capsular contracture, 3 necrosis, 4 infection/cellulitis, 1 hematoma, 1 implant rupture) which led to flap or implant failure in 5 patients. Median time to complication following reconstruction was 8 months. 32% of patients with immediate and 20% with delayed reconstruction suffered a complication, respectively. There were no local failures. V105 (P = 0.04), smoking (P = 0.02), and use of bolus (P = 0.03) were associated with increased complication rates on univariate analysis. The complication rates were 37% when V105 > 20% versus 10% when V105 < 20%; 58% in smokers versus 17% in nonsmokers; and 42% with bolus versus 7% without. Only smoking history remained significant in the multivariate analysis.Plan heterogeneity can influence the risk of reconstruction complications. Pending further validation, V105 < 20% can serve as a reasonable guide to limit this risk. Bolus should be used selectively in this setting and optimization of clinical factors such as smoking cessation can further reduce risk.