Invasive lobular carcinoma in the breast and its association with residual cancer in re-excisions and local recurrence (ISRCTN12077301)

Abstract Introduction Invasive lobular carcinoma (ILC) is a known risk factor for positive margins after breast conserving surgery (BCS). The aim of this retrospective observational study was to examine if positive margins and remaining cancer cells in the surgical specimen after re-excision are associated with locoregional recurrence. Method Female patients (>18 years) undergoing BCS for ductal cancer in situ (DCIS) or invasive cancer at site A 2015-2017 and site B 2017 were included in the study. BCS with positive margin were identified, data on residual cancer in re-excised specimens collected from patient journals and validated through the National quality register for breast cancer. The primary endpoint was locoregional recurrence-free interval (LRFi). Result 777 patients, median age 63 years (interquartile range (IQR) 53-70), undergoing BCS (65% breast cancer of no specific type (NST), 12 % ILC, 12% DCIS, and 11% other invasive/in situ) were included. The median follow-up time for recurrence-free survivors was 7.0 years (IQR 6.2-8.0). 34 (4.4%) patients developed locoregional recurrence and no evidence for difference in LRFi by positive margins and remaining cancer cells was observed (P> 0.9). 133 patients (17%) had positive margins, 131 accepted re-excision of whom 81 (61%) had remaining cancer cells (15% NST, 26% ILC, 54% DCIS and 5% other invasive/in situ). 17 (13%) again had positive margins at re-excision and accepted additional surgery. Discussion Positive margins and remaining cancer cells in re-excisions were not found to be associated to LRFi. Re-excision after non-radical BCS did not achieve clear margins in one tenth of the patients.