Purpose: Autologous breast reconstruction is a valuable option for many patients. Yet, various clinical factors, including cancer laterality, post-mastectomy radiation therapy, and tissue expander (TE) placement plane, may cause variations in the quality of the recipient internal mammary arteries and veins (IMA/IMV). Notably, prepectoral TE placement is increasingly used to minimize complications and improve postoperative outcomes. However, the biomechanical benefit of staging prepectoral TE over traditional subpectoral TE is not well understood. We aimed to clinically and histomorphometrically correlate the impact of TE location and other clinical factors on IMAs/IMVs.
Methods: We conducted a multicenter prospective cohort study of 41 patients (75 breasts) undergoing autologous flap reconstruction across two institutions between February 2020 and August 2023. Patients were categorized into five groups: 1) prepectoral TE, non-irradiated, 2) prepectoral TE, irradiated, 3) subpectoral TE, non-irradiated, 4) subpectoral TE, irradiated, or 5) no TE (control). Three- to four-millimeter full-thickness segments of bilateral IMAs/IMVs were obtained intraoperatively. Patient demographics and intraoperative details were abstracted from the medical record. To assess vessel fibrosis, remodeling, and inflammation, we measured vessel thicknesses with Masson’s trichome stains, elastin/collagen ratios with VVG stains, and smooth muscle actin percents and CD68 macrophage counts with murine monoclonal antibody. Vessel differences were evaluated based on laterality relative to the cancer, radiation history, and TE placement plane.
Results: Demographic and intraoperative details did not vary significantly between patients. Vessel laterality to the cancer alone was not associated with differences in histomorphometric outcomes (p>0.05). Radiation was associated with greater thickness in both ipsi- and contra-lateral IMVs compared to IMVs in patients whose breasts were not radiated (ipsilateral radiation: 111 µm, contralateral radiation: 126 µm, non-radiated: 77 µm; p=0.02). Compared to vessels from prepectoral TE or no TE breasts, IMAs from subpectoral TE breasts contained significantly more macrophages (subpectoral: 18, prepectoral: 10, no TE: 9; p=0.02). IMAs and IMVs from subpectoral TE breasts also had significantly higher intima thickness (subpectoral: 25 µm, prepectoral: 12 µm, no TE: 10 µm; p<0.05) and vein thickness (subpectoral: 133 µm, prepectoral: 81 µm, no TE: 75 µm; p<0.05) compared to prepectoral or no TE breasts.
Conclusions: Subpectoral TE placement before autologous breast reconstruction was associated with higher IMA macrophage counts and increased IMA/IMV wall thickness, suggesting greater inflammation, fibrosis, and vessel remodeling. Pursuing prepectoral TE placement for staged autologous breast reconstruction after mastectomy may preserve recipient vessel morphology and reduce poor postoperative outcomes. Future research may examine the clinical impact of increased recipient vessel inflammation and fibrosis.