2723 - Complications of Post-Mastectomy Radiotherapy in Immediate Two-Stage Implant Reconstruction: Contemporary Outcomes at an Academic Hospital System

M. D. Riina¹, E. Berlin¹, N. K. Taunk¹, S. Azoury², J. Serletti², and G. M. Freedman¹; ¹Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, ²Division of Plastic Surgery, Hospital of the University of Pennsylvania, Philadelphia, PA

Purpose/Objective(s): Post-mastectomy radiotherapy (PMRT) after immediate two-stage implant reconstruction has been historically associated with significant risk for complications and implant failure. However, improvements in PMRT and plastic surgery techniques and their coordination together may be reducing these risks. To address limited data in the modern era, we studied outcomes after PMRT in these patients and identified risk factors for complications. Materials/

Methods: This IRB-approved, retrospective study included patients who underwent mastectomy with immediate two-stage implant reconstruction followed by PMRT for a unilateral primary breast cancer at our institution from 2012-2021 with =3 months follow-up. Major reconstruction complications (MRC) included infection requiring washout, capsular contracture (CC) requiring capsulotomy or explantation, implant exposure, implant rupture, and hematoma/seroma (H/S) requiring surgical drainage. Reconstruction failure (RF) was defined as tissue expander (TE) or permanent implant (PI) removal without immediate replacement. Absolute reconstruction failure (ARF) was defined as RF with no further attempts at reconstruction. Logistic regression was used to identify risk factors for MRCs or RF and significant variables were included in a multivariate analysis.
Results: 190 patients met criteria for inclusion. Median follow-up was 29 months. 19.0% of patients experienced an MRC. Individual MRC rates were: infection (5.3%), CC (10.5%), exposure (5.3%), rupture (1.6%), and H/S (1.6%). The risk of an MRC was higher in patients who had PMRT to the TE rather than the PI (OR = 2.9, p = 0.02) and in patients with active smoking (OR = 6.3, p = 0.02), both of which remained significant on multivariate analysis. RF occurred in 14.2% of patients and ARF occurred in 5.3% of patients. Causes of RF are shown in Table 1. RF was more common in patients who had PMRT to the TE rather than the PI (OR = 4.0, p = 0.01) and in those actively smoking (OR = 5.0, p = 0.04) with PMRT to the TE rather than the PI remaining significant on multivariate analysis. Implant infection was commonly severe with 62.5% requiring washout and was strongly associated with RF (OR = 15.4, p < 0.001). PMRT modality (3D, intensity-modulated, proton-beam) was not associated with MRCs or RF.
Conclusion: PMRT in immediate two-stage implant reconstruction at our institution in the modern era carries an acceptably low risk of 19% MRCs and 14% RF. PMRT to the TE rather than the PI and active smoking increase the risk for both MRCs and RF. Implant infection was the most common cause of RF and most patients with infection experienced RF.

Abstract 2723 – Table 1

Reconstruction Failure Causes	N (%)
Infection	9 (33%)
Capsular Contracture	7 (26%)
Implant Exposure	5 (19%)
Breast Pain	2 (8%)
Patient Preference	2 (8%)
Radiation Dermatitis	1 (4%)
Multifactorial	1 (4%)