Analysis of Radiation Modality and Timing on Complication Rates in Breast Cancer Patients Receiving Two-Stage Expander/Implant Reconstruction.

Purpose/Objective(s) Two stages expanders/Implant (TE/I) is a common reconstruction approach for breast cancer patients. Modality and Timing of radiation (RT) in relation to the exchange surgery of expanders to implant remains controversial. Materials/Methods After IRB approval, we analyzed 661 patients who underwent immediate TE/I with and without (RT) at our institution from 2000-2019. Patients were divided to No radiation (NR), Radiation to expanders before exchange to implants (RTE) and Radiation to Implants after exchange surgery (RTI). RT was delivered either with 3D conformal photon +/- electron boost (EB) or proton therapy. Primary endpoints were reconstruction complications incidence rates across groups 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 was done to explore impact of different RT modalities on complications and local control. Logistic regression and Cox models were used. Results Median follow-up was 7.2 years. 352/661 (53.2%) didn't receive RT, 309/661 (46.7%) received RT. Among the latter, 220/309 (71.1%) received RTE before exchange and 89/309 (28.9%) received RTI after exchange. Additionally, 146/309 (47.2%) received No EB, 146/309 (47.2%) received EB and 17/309 (5.5%) received protons. There was no significant difference in tumor characteristics between RTI and RTE. The 5-year cumulative incidence of any complications was 19%, 38%, 34% in NR, RTE and RTI groups respectively. The complications proportions among RTE vs RTI cohorts were 22.7% vs 15.7% for I/N, 13.6% vs 19.1% for CC and 39.5% vs 31.5% for ORF, respectively. Among Proton patients, 8/17 (47%) developed CC compared to 16.4% (24/146) and 10.3% (15/146) in EB and NO EB groups, respectively. Also, 52.9%, 41.8% and 30.8% suffered from overall reconstruction failure in proton, EB and No EB groups, respectively. Adjusted multivariable analysis showed no difference between RTI and RTE in terms of infection/necrosis and capsular contracture. Yet, RTE remained significantly associated with overall reconstruction failure compared to RTI (39.5% vs 31.5%; OR 2.11; P = 0.02). in multivariable analysis, protons were significantly associated with CC requiring capsulotomy compared to both EB and NO EB groups (OR: 5.4, P = 0.01; and OR:10.9 P Conclusion Early radiation to the expander before the exchange to implant significantly increased overall reconstruction failure without improving local control. Protons significantly increased capsular contracture rates and overall reconstruction failure leading to more revision surgeries.