Abstract P3-18-17: Impact of change in margin negative guidelines for breast cancer on recurrence rates: Single institution audit

Abstract

Abstract Introduction: A positive resection margin after breast conserving treatment (BCT) is one ofmost important risk factor for tumour recurrence. The appropriate negative margin widthpost BCS for both ductal carcinoma in situ (DCIS) and invasive carcinoma (IC) has seen a shifttowards conservation in guidelines. In 2014, consensus guidelines based on a metaanalysis,defined a negative margin as no ink on tumour for IC and 2mm for DCIS.Methodology: We conducted a retrospective audit of patients who underwent BCS at ourinstitute in 2013 and 2016, pre and post change of guidelines and evaluated the impact onrisk of recurrence. We included all cases operated upfront and post neoadjuvantchemotherapy (NACT). Patient demographic, clinicopathological data and follow up datawas obtained from the hospital electronic medical records. Pathological evaluation ofmargins considered negative in 2013 included IDC more than 2 mm and DCIS more than 5mm away, while in 2016 a negative margin was defined as no tumour on ink for IC and morethan 2 mm for DCIS.Results: A total of 1259 women underwent BCS at our institute in 2013 and 2016 with atotal 6.6% (83/1259) margin positivity rate (MPR). In 2013 the MPR was 8.5%(52/610),9.8%(38/388) in upfront BCS (BCS) and 6.3%(14/222) in BCS post NACT (yBCS). In 2016 theMPR was 4.8%(31/649), 5.3%(20/377) in BCS and 4%(11/272) in yBCS In 2016 an additional7.5%(49/649) would qualify as margin positive based on previous guidelines. In the overallcohort the median age was 46 years, median T size 3.1 cm, 11% had microcalcification onmammogram outside the lesion (micro+), 88.24% BIRADS B/C density, 85.9% grade 3, 96.3%IDC, 1.2% ILC,2.5% DCIS and 56.71% lymph node negative cancers. The median follow up ofthis cohort was 65.25 months. The 5 Year local recurrence free survival (LRFS) and diseasefree survival (DFS) was 94.6% (95%CI 92.64-96.669) vs 94.7% (95%CI 92.74-96.66) and 84.9%(95%C 81.96-87.84) vs 81.9 (95%CI 78.70-85.04) for 2013 and 16 respectively (p=NS forboth). On multivariate cox regression analysis factors associated with increased risk of localrecurrence (LR) were surgery done Upfront vs post NACT (HR 3.35, 95% CI 1.76-6.26,p=0.0001) MPR (HR 2.76, 95% CI 1.27-5.98, p= 0.01) and presence of micro+ (HR 2.63, 95%CI 1.38-5.03, p=0.003). Mammogram density, EIC and year of surgery had no impact on LR.While age ( HR 0.98, 95% CI 0.96-0.99 p=0.004), lymph node positive (HR 2.48, 95%CI 1.82-3.37, P< 0.0001), higher grade (HR 2.11, 95% CI 1.18-3.79, p=0.012), MPR (HR 1.73, 95% CI1.03-2.90, p=0.037)and surgery done upfront vs post NACT (HR 2.64, 95%CI 1.88-3.74,p=<0.0001) were associated with worse DFS.Conclusion: Wider negative margins do not improve local control for DCIS or invasivecarcinoma in women undergoing BCT. Accurate mapping of the extent of disease andobtaining a negative margin should be carefully evaluated in all cases undergoing BCS.Change in definition is well supported by our audit and appears safe to apply to even highergrade and poorer biology tumours. Citation Format: Sridevi Rishabh Murali-Nanavati, Nita Nair, Rohini Hawaldar, Vani Parmar, Tanuja Shet, Shabina Siddique, Vaibhav Vanmali, Shalaka Joshi, Rajendra Badwe. Impact of change in margin negative guidelines for breast cancer on recurrence rates: Single institution audit [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-17.