Factors Influencing Residual Glandular Breast Tissue after Risk-Reducing Mastectomy in Genetically Predisposed Individuals Detected by MRI Mammography

SIMPLE SUMMARY: Residual glandular tissue (RGT) after risk-reducing mastectomy in patients with a familial predisposition (high-risk collective) is associated with a risk of breast cancer that cannot be precisely determined. The residual risk should be as assessable as possible. For this purpose, a monocentric retrospective analysis of measurable factors influencing the postoperative residual glandular tissue was performed. Analyzed were 117 breasts, 63 left and 54 right, from a cohort of 81 patients (carriers of a pathogenic mutation) with unilateral (36 patients) or bilateral (45 patients) risk-reducing mastectomy. Consultation and possible testing were performed with the patient’s consent at the FBREK (Familial Breast and Ovarian Cancer) Center of the University Hospital Düsseldorf (UKD), or in advance at another site of the German Consortium for Familial Breast and Ovarian Cancer. MRI-assisted detection of residual skin flap thickness and volumetry of each breast were performed. Residual glandular tissue was recorded volumetrically. In addition, patient-related covariates were recorded, and their influence on postoperative residual glandular tissue and skin flap thickness was analyzed using univariate and multivariate regression. ABSTRACT: Purpose: This study seeks to evaluate MR imaging morphological factors and other covariates that influence the presence of residual glandular tissue after risk-reducing mastectomy in patients with a familial predisposition. Methods: We analyzed women of a high-risk collective with pathogenic mutation (BRCA1 (n = 49), BRCA2 (n = 24), or further mutation (n = 9)). A total of 117 breasts were analyzed, 63 left and 54 right, from a cohort of 81 patients, who were on average 40 years old. The mean follow-up was 63 months (range 12–180 months, SD = 39.67). Retrospective analysis of MR imaging data from 2006–2022 of patients of a high-risk collective (all carriers of a pathogenic mutation) with contralateral (RRCM) or bilateral risk-reducing mastectomy (RRBM) was performed. In the image data the remaining skin flap thickness by distance measurements at eight equally distributed, clockwise points and the retromamillary area, as well as by volumetry of each breast, was elected. Residual glandular tissue was also volumetrized. In addition, patient-related covariates were recorded and their influence on postoperative residual glandular tissue and skin flap thickness was analyzed by uni- and multivariate regressions. Results: A significant association with postoperative residual glandular tissue was shown in multivariate analysis for the independent variables breast density, skin flap mean, and surgical method (all p-values < 0.01). A negatively significant association could be seen for the variables preoperative breast volume (p-values < 0.01) and surgeon experience (most p-values < 0.05–<0.1). Conclusion: Postoperative residual glandular tissue is an important tool for quantifying the risk of developing breast cancer after risk-reducing mastectomy. Different effects on residual glandular tissue were shown for the independent variables breast density, skin flap, surgical method, preoperative breast volume, and surgeon experience, so these should be considered in future surgical procedures preoperatively as well as postoperatively. Breast MRI has proven to be a suitable method to analyze the skin flap as well as the RGT.