D100. Radiate The Flap or Expander? The Impact of Post-Mastectomy Radiation Timing on Overall Outcomes after Autologous Free Flap Breast Reconstruction

Abstract

PURPOSE: Optimal timing of post-mastectomy radiation therapy (PMRT) in autologous breast reconstruction is controversial. Our study compares overall reconstructive outcomes in patients requiring post-mastectomy radiation therapy where either the expander or the free flap was radiated. METHODS: A single-center retrospective review was performed for patients who underwent free flap breast reconstruction and post-mastectomy radiation from January 2004 through January 2021. Demographic, intraoperative, and post-operative variables were recorded. RESULTS: 452 free flaps were identified, and 82 underwent PMRT. 59.8% were radiated with an expander prior to free flap surgery (PreDIEP), and 40.2% flaps underwent PMRT (PostDIEP). PostDIEP patients were significantly younger (43.0 vs 47.9years, p=0.016). Radiation was performed 454.0±231.3 days prior to DIEP, versus 220.3±325.9 days after DIEP (p=0.000). There were no significant differences in free flap outcomes between the two cohorts including thrombosis, venous congestion, flap loss, takebacks, fat necrosis, seroma, or infection. However, there were significantly more total reconstructive complications, including infection and wound breakdown, experienced by the PreDIEP cohort (46.9% versus 24.2%, p=0.038). Mean follow up after DIEP was 1.9 years. CONCLUSION: Timing of PMRT did not impact free flap outcomes, but those who had the expander radiated experienced significantly more complications overall. For the 30.6% of patients in the preDIEP group who always intended to undergo autologous reconstruction, radiation after flap may have improved their overall outcomes. As added complications cause delays in cancer therapy and final reconstruction, our results suggest that PMRT of the flap when possible may improve the overall experience for breast cancer patients.