Abstract P2-01-02: Methods impacting the false negative rate of sentinel lymph node surgery in patients presenting with node positive breast cancer (T0-T4,N1-2) who receive neoadjuvant chemotherapy – Results from a prospective trial – ACOSOG Z1071 (Alliance)
Authors: Boughey Judy C , Ballman Karla V , Symmans William F , McCall Linda M , Mittendorf Elizabeth A , Ahrendt Gretchen M , Wilke Lee G , Taback Bret , Hunt Kelly K 
Published: May 2015

Abstract
Background: The American College of Surgeons Oncology Group (ACOSOG) Z1071 trial (Alliance) reported a false negative rate (FNR) of 12.6% with sentinel lymph node (SLN) surgery after neoadjuvant chemotherapy in women presenting with node-positive breast cancer. Proposed methods to decrease the FNR include clip placement in the positive node at initial diagnosis with confirmation of resection of the clipped node at surgery and inclusion of residual metastatic cells identified by immunohistochemistry (IHC) for cytokeratins and disease measuring &lt;0.2mm on H&E in the definition of node positivity after chemotherapy. Herein we evaluate the impact of these methods on FNR.
Methods: Z1071 was a prospective multi-institutional trial in which women with clinical T0-4,N1-2,M0 breast cancer underwent both SLN surgery and axillary dissection (ALND) after neoadjuvant chemotherapy. The primary endpoint defined nodal metastasis as disease &gt;0.2mm on H&E. Slides were submitted for central IHC staining when H&E-negative, unless performed locally. For this analysis, we expanded the definition of node positivity to include metastases less than 0.2mm on H&E and metastatic deposits identified by IHC.
In 171 cases, a clip was placed in the node at initial biopsy and in these cases the SLNs and ALND were evaluated by x-ray or pathology to document clip location. FNR in the clip cohort is reported using the primary endpoint definition of node positive disease (&gt;0.2mm on H&E).
Results: In the 113 cases where the clip was found in the SLN the FNR was 6.4% (1.8-15.5%). In the 29 cases where the clip was found in the ALND specimen, the FNR was 22.2% (6.4-47.6%).
IHC was available on 470 of 525 patients with cN1 disease and 2 SLNs resected. Using the definition of H&E metastasis &gt;0.2mm, the FNR in these patients was 11.3% (34/301, 8.0-15.4%) which decreased to 8.7% (27/311, 5.6-11.8%) when including any disease &lt;0.2mm. SLNs from 16 patients had disease &lt;0.2mm in size. Seven patients previously classified as false negative SLN changed to true positive with identification of disease in the SLN. Nine patients changed from node-negative to node-positive with the only disease being &lt;0.2mm disease found in the SLN. Nodal pathologic complete response rate changed from 36.0% to 33.8% with the inclusion of metastases &lt;0.2mm.
NResidual disease identified in SLNs or ALNDFNR (%)95% CINode positive definitionSLN metastases &gt;0.2mm by H&E470301 (64.0%)11.38.0-15.4SLN metastasis any size on IHC or H&E470311 (66.2%)8.75.6-11.8Clip locationClip in SLN11462 (54.4%)6.41.8-15.5Clip in ALND2918 (62.1%)22.26.4-47.6Clip location unknown2920 (69.0%)14.33.0-36.3Clip not placed354207 (58.5%)13.59.1-18.9
Conclusion: Placement of a clip at initial diagnosis of node positive disease with identification of the clip during the SLN surgery reduces the FNR. Use of IHC with inclusion of metastases &lt;0.2mm in the definition of residual nodal disease in women with node positive breast cancer after chemotherapy also improves the accuracy of SLN surgery. Use of one or both of these methods should be considered when performing SLN in this setting.
Citation Format: Judy C Boughey, Karla V Ballman, William F Symmans, Linda M McCall, Elizabeth A Mittendorf, Gretchen M Ahrendt, Lee G Wilke, Bret Taback, Kelly K Hunt. Methods impacting the false negative rate of sentinel lymph node surgery in patients presenting with node positive breast cancer (T0-T4,N1-2) who receive neoadjuvant chemotherapy – Results from a prospective trial – ACOSOG Z1071 (Alliance) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-01-02.