Abstract ES7-1: Methods to minimize the false negative rate of sentinel lymph node surgery after neoadjuvant chemotherapy for node positive breast cancer

Neoadjuvant chemotherapy (NAC) is known to decrease the extent of disease in the breast and increase rates of breast conservation. In addition, NAC also can reduce the likelihood of nodal positivity and hence decrease need for axillary node dissection and its associated morbidities. Three prospective clinical trials have assessed the false negative rate (FNR) of SLN after NAC for patients with clinically node-positive disease at presentation. The American College of Surgeons Oncology Group (ACOSOG) Z1071 study reported a false negative rate (FNR) of SLN surgery of 12.6% in patients with cN1 disease with 2 or more SLNs resected. The FNR was lower at 10.6% when dual tracer technique was utilized. Additional analysis showed that when a clip was placed in the positive node at diagnosis and the clipped node was resected as one of the SLNs, the FNR was 6.8%. The Canadian study (SN FNAC - sentinel node following neoadjuvant chemotherapy) reported a FNR of 13.3% when defining SLN with isolated tumor cells (ITC) as negative and 8.4% when including ITC in the definition of a positive SLN. The SENTINA study from Europe reported an overall FNR of 14.2%, however when excluding patients with only a single SLN removed the FNR was 9.8%. Further work with preoperative localization of the clipped node with a seed and resection of the localized clipped node along with the sentinel nodes (termed targeted axillary dissection) has been shown to have a FNR of 2.4%. Surgeons are incorporating SLN after NAC into their clinical practice for patients with a good response to NAC and thus use of SLN surgery after NAC for patients with node-positive breast cancer is increasing. There are multiple methods that can decrease the FNR of the procedure in this setting. These include use of dual tracer for SLN identification, resection of the initial biopsy-proven positive node, resection of at least 2 SLNs and use of immunohistochemical staining of the SLNs. There are several different techniques to assist with ensuring resection of the initially biopsy-proven positive lymph node which include varying methods to mark the node at diagnosis and ways to identify the node at time of SLN surgery. The node can be marked at the time of percutaneous lymph node biopsy (or at a subsequent visit prior to initiation of NAC) with a clip, a radioactive seed, or tattooed with ink. At the time of surgery, if ink or a radioactive seed was placed, the node can be identified using these techniques at the time of axillary surgery. If a clip was placed at diagnosis, this can undergo preoperative localization, with a radioactive seed or wire, to maximize likelihood of identifying the clipped node during surgery. For patients with biopsy-proven node-positive breast cancer, SLN surgery after NAC allows assessment of residual nodal disease and can enable patients who have their axillary disease eradicated by NAC to avoid ALND. Citation Format: Boughey J. Methods to minimize the false negative rate of sentinel lymph node surgery after neoadjuvant chemotherapy for node positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr ES7-1.