Comparison between Pre-Pectoral and Post-Pectoral Implant Reconstruction and Different Radiation Modalities on Breast Reconstruction Complications

Abstract

Single Stage direct to implant (DTI) is a rising reconstruction approach. It has been speculated that prepectoral implant placement reduces reconstruction complications as well as using newer postmastectomy radiation (PMRT) modalities as protons. Largest series in this topic included 350 DTI patients with less than 30 patients receiving PMRT. We reviewed the charts of 2,187 patients (pts) who underwent mastectomy and reconstruction at our institution between 2000 and 2020. Pts only receiving DTI with and without PMRT were included. PMRT was delivered either with 3D conformal photon +/- chest wall electron boost (CWB) or proton therapy mainly with pencil beam scanning. All pts received conventional fractionation (50-50.4 Gy in 25-28 fractions). Patients on active protons clinical trials were excluded. Primary endpoints were reconstruction complications defined as infection/necrosis (I/N) requiring debridement; capsular contracture (CC) requiring capsulotomy and overall reconstruction failure (ORF: removal of permanent implant for any complication with and without salvage reconstruction). Subgroup analysis for pts receiving PMRT was done to explore impact of proton and photons on complications. Logistic and cox regression were used. Eight hundred nine pts received DTI, with an overall median follow-up of 6.2 years. Among the entire cohort, 78/809 (9.7%) had prepectoral implants while the rest had subpectoral implants with and without alloderm support. Of the entire cohort 391/809 (48.5%) received PMRT, among those 43/391 (11%) received protons. The 5 years cumulative incidence of CC was 8.5% and 6.6% among prepectoral vs subpectoral implants (HR = 1.2, p = 0.7). The 5 years cumulative incidence of ORF was 32.2% and 28.2% among prepectoral vs subpectoral implants (HR 1.1, p = 0.6). For pts receiving PMRT, the 5 years cumulative incidence of CC were 26.0% and 8.6% among protons vs photons (HR 3.7, p < 0.0005). The 5 years cumulative incidence of ORF were 38.2% and 30.1% among protons vs photons (HR 1.4, p = 0.2). Multivariable logistic regression analysis accounting for BMI, smoking history, diabetes, and PMRT showed no significant difference between prepectoral implants versus subpectoral coverage for CC (OR = 0.7, p = 0.5), and for ORF (OR = 0.9, p = 0.8). Subgroup multivariable analysis for those receiving PMRT only showed protons compared to photons significantly increased the risk of CC (OR = 5.3, p < 0.0001) and ORF (OR = 2.1, p = 0.03). No significant difference in I/N was noted between photons and protons or between prepectoral and subpectoral pts. For breast cancer patients receiving single stage direct to implant reconstruction with and without PMRT, prepectoral implant placement did not reduce the risk of complications. Proton therapy compared to photons significantly increased the risk of capsular contracture requiring capsulotomies and significantly increased overall reconstruction failures with implants removal.