Impact of Revised Margin Negative Guidelines in Breast Cancer on Survival: Single Institution Audit

A positive resection margin after breast conserving surgery (BCS) is one of most significant risk factors for tumour recurrence. Guidelines have shifted toward more conservative approaches regarding the appropriate negative margin width after BCS for both ductal carcinoma in situ (DCIS) and invasive carcinoma (IC). In 2014, consensus guidelines based on a metanalysis, defined a negative margin as no ink on tumour for IC and 2 mm for DCIS. We conducted a retrospective audit of patients who presented with clinically palpable tumours and underwent BCS at our institute in 2013 and 2016, both before and after change of guidelines and evaluated its impact on margin revision and local recurrence. We included all cases operated upfront and post neoadjuvant chemotherapy (NACT). Patient demographic, clinicopathological data, and follow-up data were obtained from the hospital electronic medical records. Pathological evaluation of margins considered negative in 2013 included IC more than 1 mm and DCIS more than 5 mm away, while in 2016, a negative margin was defined as no tumour on ink for IC and more than 2 mm for DCIS. A total of 1259 women underwent BCS at our institute in 2013 and 2016, with a total margin positivity rate (MPR) of 6.6% (83/1259) with a total 6.6% (83/1259) margin positivity rate (MPR). In 2013, the MPR was 8.5% (52/610), 9.8% (38/388) in upfront BCS and 6.3% (14/222) in BCS post NACT (yBCS). In 2016 the MPR was 4.8% (31/649), 5.3% (20/377) in BCS and 4% (11/272) in yBCS in 2016. In 2016, the new guidelines helped avoid margin revision in 18.48% (120/649) of cases. The median follow-up of this cohort was 65.25 months. The 5-year local recurrence-free survival (LRFS) was 94.6% (95%CI 92.64–96.669) vs. 94.7% (95%CI 92.74–96.66) for 2013 and 16 respectively ( p = NS for both). On multivariate cox regression analysis factors associated with an increased risk of local recurrence (LR) included the timing of surgery (NACT vs Upfront) (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 the presence of microcalcifications (HR 1.38, 95% CI 0.64–2.98, p = 0.42). The new guidelines resulted avoiding margin revision in over 18% women with who presented with clinically palpable tumours with no detriment in local control.