Does Breast Reconstruction Affect Radiation Therapy? Examining Device Type, Placement, and Dose Effects

Background: Prepectoral breast reconstruction has surpassed subpectoral placement over the past decade, with most reconstructions being prepectoral. However, the impact of reconstruction, including type (immediate implant-based versus delayed with a tissue expander [TE]) and device position (prepectoral versus subpectoral) on radiation therapy (RT) planning is understudied. This study compares RT dose metrics and time to treatment between reconstructed and nonreconstructed cases and by reconstruction device type and placement. Methods: This single-institution study included 161 patients who underwent mastectomy or lumpectomy followed by RT from 2021 through 2024. Eighty patients were reconstructed (implants, n = 29; TEs, n = 51) and 81 were not reconstructed. Reconstruction was prepectoral ( n = 41) or subpectoral ( n = 39). Radiation outcomes included mean heart dose, volume of lung irradiated, volume of reduced dose areas (“cold spots”), volume of increased dose areas (“hot spots”), and internal mammary node (IMN) coverage. Additional outcomes included time to RT, IMN omission, TE deflation, and skin toxicity. Results: Prepectoral and subpectoral reconstructions were associated with increased heart dose and reduced volume of cold spots compared with nonreconstruction. Subpectoral reconstruction was associated with reduced ipsilateral lung dose versus nonreconstruction. Prepectoral devices were most frequently associated with IMN omission. No differences in time to RT, IMN coverage, TE deflations, or complications were observed. No differences were observed based on device type. Conclusions: Device position or type does not significantly affect RT plan quality. For prepectoral reconstructions, there may be additional considerations affecting IMN treatment. Reconstruction, especially subpectoral, may minimize lung dose when IMN treatment is needed.