Plastic Surgery Research Council
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PSRC 60th Annual Meeting
Program and Abstracts

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External Volume Expansion and Fat Grafting after Post Mastectomy Radiation Therapy: increased skin angiogenesis and proliferation may improve fat graft based soft tissue reconstruction
Jorge Lujan-Hernandez, M.D.1, Michael S. Chin, M.D.1, Dylan J. Perry, B.A.1, Ava G. Chappell, B.A.1, Oksana O. Babchenko, B.S.1, Elizabeth Bannon, M.S.1, Luca Lancerotto, M.D.2, Yuan Chyuan Lo, PhD1, Thomas J. Fitzgerald, M.D.1, Janice F. Lalikos, M.D.1.
1University of Massachusetts Medical School, Worcester, MA, USA, 2University of Padova, Padova, Italy.

PURPOSE:
:Post-mastectomy radiation therapy (XRT) has improved breast cancer outcomes but complicated the reconstruction process. Autologous fat grafting (FG) is an alternative to invasive reconstructive techniques, however results are currently unsatisfactory compared to non-irradiated patients. Pre-treatment with External Volume Expansion (EVE) has been proposed to improve graft take and cosmesis. EVE effects on radiation damaged tissue and its influence on fat graft take remain largely unexplored.
METHODS:
Thirty hairless mice were divided into 4 groups. 50gy of localized dorsal XRT was applied and mice were monitored for 8 weeks until development of chronic tissue fibrosis. Group 1 (n=3) received unilateral XRT with contralateral control. Group 2 (n=3) received XRT on one side and human fat (0.6cc) was grafted bilaterally underneath irradiated and non irradiated sites. Group 3 (n=12) received bilateral XRT and EVE application for 5 days unilaterally using a vacuum pump set at -25mmHg.
Group 4 (n=12) received bilateral XRT, then pre-treated with EVE on one side and bilateral FG after 2 weeks. Skin perfusion and oxygenation was measured using Hyperspectral Imaging (HSI). Fat graft volumes were quantified using 3D reconstructions from in-vivo microCT scans. Immunohistochemistry of harvested skin and grafts was performed to analyze vascularity (CD31) and cell proliferation (ki67).
RESULTS:
Group 1. Irradiated skin was 13% less perfused and hypovascular compared to control side (p<0.05).
Group 2. Fat graft volume on irradiated site was 10% inferior compared to grafted fat in non-irradiated side after 8 weeks (p<0.05).
Group 3. EVE application induced a 37% increase in vascularity (p<0.01) in the overlying skin after 5 days of stimulation, a 45% increase in proliferating cells (p<0.05), and increased skin thickness in pre-expanded irradiated side compared to unexpanded counterpart. Group 4. In progress. There will be preliminary data for the Council meeting.
CONCLUSION:
Radiation injures microvasculature and reduces skin perfusion, significantly reducing fat graft survival. EVE likely works through local hypoxia and mechanotransductive phenomena, inducing proliferation and angiogenesis of the recipient site despite radiation damage, benefitting fat graft-based reconstruction. Future studies will investigate these mechanisms further.


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