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Impact of Marging Shaving on Re-Excision rates in patients with primary invasive carcinoma and carcinoma in situ in Breast Conserving Surgery. Data from a population based cohort of clinical cancer registry
Fernandez-Pacheco M.1, Ortmann O.1, Gerken M.2, Ignatov A.1, Klinkhammer-Schalke M.2, Inwald E.C.1
1University Medical Center Regensburg, Department of Gynaecology and Obstetrics, Regensburg, Deutschland, 2Tumor Center Institute for Quality Management and Health Services Research, University of Regensburg, Regensburg, Deutschland

Background: Previous studies reported considerably high re-excision rates in breast-conserving surgery (BCS) in patients with primary invasive breast cancer or carcinoma in situ. Circumferential Marging Shaving (CMS) could be a surgical strategy to reduce re-excision rates. This study aimed to investigate the effects of CMS during BCS on reducing residual tumor.
Methods: This retrospective cohort study analyzed clinical cancer registry data from 591 patients with non-metastatic, invasive breast cancer (NST), lobular type or carcinoma in situ receiving BCS in the University Medical Center in Regensburg from January 2017 to September 2019.
Data basis: Clinical, histopathological and surgical information from the database of the Tumor Center and of the Department of Gynecology and Obstetrics of the University Medical Center in Regensburg was used.
Statistical methods and analysis: Binary Logistic Regression and Stepwise-Back-Selection of variables in the equation.
Discussion and conclusion: Our study suggests that only certain patients who underwent breast conserving surgery benefit from CMS compared to the standard technique of doing re-excision depending on intraoperative sonography/mammography. Patients with smaller tumors (pathologic T1) showed to have a significant benefit from CMS. In all other subgroups using one surgical technique or another did not offer any significant advantage. Regarding the risk of residual tumor after BCS, older patients (specially >70 years) appear to have less residual tumor than younger ones, maybe due to more extensive excisions. Also, ductal carcinoma in situ showed to have a higher risk of residual tumor as previously described in literature