|Program and Abstracts
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Effect Modifiers of Radiation Risks in Total Skin-Sparing Mastectomy with Immediate Tissue Expander-Implant Reconstruction
Frederick Wang, MD, Anne Warren Peled, MD, Barbara Fowble, MD, Michael Alvarado, MD, Cheryl Ewing, MD, Laura Esserman, MD, MBA, Robert Foster, MD, Hani Sbitany, MD.
University of California, San Francisco, San Francisco, CA, USA.
Total skin-sparing mastectomy (TSSM), with complete preservation of the nipple-areolar complex (NAC) skin and excision of nipple tissue, is a standard mastectomy procedure at our institution, and the majority of patients undergo immediate tissue expander (TE)-based breast reconstruction. Post-mastectomy radiation therapy (PMRT) remains a major risk factor for postoperative complications of infections, wound breakdown, and implant loss in these patients. We aim to evaluate the risks of complications with PMRT in our TSSM cohort and to identify potential modifiers of these risks, including body mass index (BMI) and method of TE coverage (acellular dermal matrix (ADM)-assisted, additional serratus flap, or pectoralis flap alone).
We reviewed all cases of TSSM with immediate tissue expander-based breast reconstruction between 2006-2013. Cases with prior radiation history were excluded. Patient demographics, comorbidities, surgical characteristics, and postoperative complications were collected prospectively via chart review. Outcomes were first assessed based on exposure to PMRT. A logistic generalized estimating equation (GEE) model was developed to assess interactions between PMRT, BMI, and method of TE coverage.
We identified 847 cases (510 patients) without PMRT and 131 cases (128 patients) with exposure to PMRT with median follow-up of 21 months (IQR 12-49 months). Patients who had PMRT were 4 years younger on average (p=0.002), and they were more likely to have received chemotherapy (p<0.001) or hormonal therapy (p<0.001) for treatment of higher clinical stage breast cancer (p<0.001). TSSM incisions were similar between the groups, but patients who received PMRT had fewer ADM-assisted reconstructions compared to those without PMRT (p=0.006). In unadjusted analysis, PMRT was associated with more than 10% increase in the risk and more than 2.5 times the odds of infections, wound breakdown, and implant loss. In cases without radiation therapy, those with ADM coverage had 3.5 (95% CI 1.5-8.4) times the odds of developing infections requiring procedures compared to serratus muscle coverage. In the multivariate analysis, an increase in BMI by 1 kg/m2 was associated with 0.9 (95% CI 0.8-1.0) times the odds of wound breakdown in cases with PMRT. ADM-assisted coverage was associated with 0.2 (95% CI 0.04-0.7, p=0.014) times the odds of wound breakdown and 0.2 (95% CI 0.05-0.9, p=0.035) times the odds of implant loss compared to pectoralis flap coverage alone in cases with PMRT. Similarly, serratus flap coverage was associated with 0.3 (95% CI 0.1-1.2, p=0.086) times the odds of wound breakdown and 0.1 (95% CI 0.03-0.7, p=0.019) times the odds of implant loss compared to pectoralis flap coverage alone in cases with PMRT. There was no difference between ADM and serratus flap coverage on the risk of implant loss either with or without PMRT.
In TSSM cases with immediate TE-based reconstruction, ADM-assisted coverage is associated with an increased risk of infections requiring procedures compared to serratus flap coverage in cases without PMRT. In cases with PMRT, higher BMI may decrease the risk of wound breakdown and both ADM-assisted coverage and serratus flap coverage decrease the risk of wound breakdown and implant loss compared to pectoralis flap alone.
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