LAUSR

Introduction: Post-mastectomy radiation therapy (PMRT) is an important adjuvant treatment in patients with locally advanced breast cancer, shown to decrease the rate of locoregional recurrence and improve overall survival. Autologous breast reconstruction is the standard-of-care in patients who require PMRT. However, there is no clear superior approach regarding the optimal timing of reconstruction in these patients. Our goal was to compare outcomes between patients who underwent autologous reconstruction either before or after undergoing PMRT. Methods: We performed a retrospective chart review of patients who underwent all stages of mastectomy, autologous reconstruction, and PMRT at UCSF between 2015 and 2021. Clinical and surgical characteristics and complications were collected and assessed. We then matched these patients by age, BMI and autologous reconstruction type to a cohort of patients who underwent both mastectomy and autologous reconstruction at UCSF who did not require PMRT. Groups were compared by both timing of and receipt of radiation. Results: Nineteen patients underwent mastectomy, autologous reconstruction, and PMRT at UCSF between 2015 and 2021. Thirteen of these patients underwent reconstruction after receiving PMRT, while six of these patients underwent reconstruction followed by PMRT. These nineteen patients were matched by age, BMI and flap type to a cohort of 19 patients who underwent mastectomy and autologous reconstruction at UCSF. The cumulative early complication rate was 16% in the radiated group and 21% in the non-radiated group. This included infection requiring IV antibiotics, hematoma, wound breakdown, mastectomy flap necrosis, and arterial or venous thrombosis [see Table 1 for breakdown by group]. No flap loss occurred in any group. Fat necrosis was observed in 16% of radiated patients and 11% of non-radiated patients. Revision rates were equal between the radiated and non-radiated groups at 58% (including currently planned revisions). There was no strong correlation between complication rate and either total radiation dose or time between radiation and reconstruction (r=-0.5 and r=-0.1). Discussion: Complication rates between all groups were similar. Notably, the only observed infections, both requiring admission and IV antibiotics, occurred in the pre-reconstruction PMRT group. Given the potential for tissue expander infection and increased number of outpatient visits, further investigation is warranted in immediate autologous reconstruction in those patients who require PMRT, not only to decrease the hospital and patient burden, but to improve patient satisfaction. Larger cohort studies are required to draw further conclusions on the effect of PMRT and timing of autologous reconstruction, and to investigate patient-reported outcomes. Table 1.Complication rate by groupComplicationRadiated. Pre-recon PMRT. Post-recon PMRTNon-radiatedCumulative early complications16%. 15%. 17%21%Infection11%. 16%. 0%0%Hematoma0%. 0%. 0%5%Wound breakdown11%. 8%. 17%5%Mastectomy flap necrosis5%. 0%. 17%11%Arterial or venous thrombosis0%. 0%. 0%5%Fat necrosis16%. 15%. 17%11%Revision58%. 62%. 50%58% Citation Format: Laura Barnes, Deborah Martins, Merisa Piper. Timing of post-mastectomy radiation therapy and autologous reconstruction outcomes: A retrospective review [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-21-03.