Abstract P4-02-09: Factors affecting the number of sentinel lymph nodes removed in the treatment and staging of breast cancer?
Authors: Dixon J Michael , Grewar Julia , Twelves Dominique , Kay Charlene , Martinez-Perez Carlos , Meehan James , Gray Mark , Turnbull Arran K 
Published: March 2020

Abstract
Background: A sentinel lymph node in breast cancer surgery is defined as a blue node or a “hot” radioactive node and includes nodes other than the hottest node providing that they contain at least 10% of the radioactivity of the hottest node. The false negative rate of SLNB in breast cancer surgery falls as the number of sentinel nodes removed increases. A recent large US study suggested that patients having 3 or more nodes removed had a better overall survival. Substantial variation remains in how many nodes surgeons remove and what constitutes an adequate SLNB. The aim of this study was to identify what factors influence the number of lymph nodes removed by SNLB.
Methods: Data were collected retrospectively from 426 patients with breast cancer who underwent sentinel lymph node biopsy at the Edinburgh Breast Unit by 10 different surgeons between March 2016 and September 2017. Patients with imaging and core biopsy-diagnosed invasive or in situ breast cancer who underwent SLNB as part of breast conserving surgery or mastectomy were eligible. Factors included were patient age, tumour size, tumour grade, type of surgery and surgeon, neoadjuvant chemotherapy (NACT), lympho-vascular invasion, hormone and HER2 receptor status and the number of positive nodes (defined by histological assessment). Univariate and multivariable statistical analyses were performed.
Results: The number of sentinel nodes biopsied varied significantly between operating surgeon (p&lt;0.0001) and was significantly associated with the number of positive nodes (p&lt;0.0001), patient age (p=0.037), tumour size (p=0.011) and the use of NACT (p&lt;0.003) in multivariable analysis. More nodes were removed in patients who had node-positive disease, were younger, had larger tumours and had neoadjuvant chemotherapy. Within the subset who received NACT (n=40), separate multivariable analyses were performed for both the 30% of these patients who were lymph-node positive at diagnosis and the 70% who were not. No factors were found to be significant explanatory variables for the number of SLNs biopsied in the group who were lymph-node negative at diagnosis. In contrast, although the number of patients who received NACT and were lymph-node positive at diagnosis was small, surgeon was found to be a statistically significant explanatory variable for the number of SLNs taken at biopsy.
Discussion:
• This study shows that the surgeon plays an important and significant role in determining the number of sentinel nodes removed by sentinel lymph node biopsy.
• The number of positive nodes was also found to be an important factor, likely due to greater numbers of nodes being taken by surgeons who suspect positive nodes on intraoperatively inspection.
• Higher numbers of nodes were removed in younger patients, patients with larger tumours and patients who received NACT.
• In conclusion, either some surgeons remove too many nodes or others are removing too few and there needs to be more consistency in surgical SNB practices.
Citation Format: J Michael Dixon, Julia Grewar, Dominique Twelves, Charlene Kay, Carlos Martinez-Perez, James Meehan, Mark Gray, Arran K Turnbull. Factors affecting the number of sentinel lymph nodes removed in the treatment and staging of breast cancer? [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-02-09.