Neoadjuvant chemotherapy in breast-conserving surgery - Consequences on margin status and excision volumes: A nationwide pathology study

Neoadjuvant chemotherapy (NACT) is increasingly used in patients with operable disease due to the potential of converting patients requiring mastectomy to breast conserving surgery (BCS) or lowering resection volumes to improve cosmetic outcome. This nationwide retrospective study aims to determine margin status and specimen volume in patients with invasive breast cancer who underwent BCS after NACT. All patients who underwent BCS in 2012-2013 for invasive breast cancer were selected from a nationwide network and registry of histology and cytopathology in the Netherlands (PALGA). Of the 9901 patients, 626 (6.3%) received NACT. After primary surgery 949 (10.2%) patients had tumour-involved margins compared to 152 (24.3%) after NACT. Close margins (≤1 mm) were seen in another 111 (17.7%) patients after NACT. The adjusted odds ratio for involved margins after NACT was 2.94, meaning a three times higher risk of involved margins compared with primary surgery. In patients with lobular carcinoma (54.9%) and no response to NACT (42.1%) higher tumour-involved margins were seen. High resection volumes >60 cc were observed in 224 (36%) patients after NACT of which 37 (16.5%) had tumour involved margins and 32 (14.3%) close margins ≤1 mm. The primary goal of the surgeon performing BCS after NACT, to reach tumour-free margins, is not accomplished in one out of four patients. Patients especially at risk are patients with ILC and no pathological tumour response. Excessive resection volumes after NACT do not guarantee tumour-free margins. Further research is necessary to analyze whether we are counterproductive when NACT is given in order to lower resection volumes.