Abstract P1-15-13: Sentinel lymph node biopsy after neoadjuvant chemo therapy in patients with clinically node negative breast cancer: Can sentinel lymph node biopsy be omitted in selected tumor subtypes?
Authors: Beijert IJ , Francken A , Honkoop AH , Noorda EM 
Published: May 2019

Abstract
Background
Selected patients presenting with clinically node negative breast cancer (cN0) stage II-III can be treated with neoadjuvant chemo therapy (NCT) followed by surgery of the breast and sentinel lymph node biopsy (SLNB). Pathological response rates are known to vary by tumor subtype with complete pathological response up to 60% in both ER-, HER2-positive tumors and triple-negative (TN) tumors. However, hormone receptor-positive, HER2-negative tumors exhibits lower response rates to NCT. About 70-80% of the patients with a clinically negative axilla, also have pathologically negative axilla after NCT. Properly selecting those patients with a low probability of sentinel lymph node (SLN) metastasis after NCT might save them an unnecessary SLNB. The aim of our study was to assess the impact of tumor subtypes on final pathologic node (pN) status in patients with clinically node negative (cN0) breast cancer who underwent NCT.
Methods
All cN0 patients diagnosed from 2014-2017 in one large teaching hospital in the Netherlands who were treated with NCT and subsequent surgery including SLNB were selected. This retrospective cohort contained a series of 107 patients with 105 tumors treated for stage II-III breast cancer resp. stage 2 (n=107) and stage 3 (n=2), all cN0. Patient age, tumor size, uni/multifocality at presentation did not differs across subtypes. Histological grading and histological type at presentation did differ across subtypes. Approximated subtype was TN in 21 (19.3 %), HER2-positive in 34 (31.2%), and hormone-receptor-positive, HER2-negative in 54 (49.5%) patients.
Results
In a total of 109 tumors, 88 had a negative post-NCT SLNB (80.7%), 4 had isolated tumor cells (3.7%) 7 had micro metastasis (6.4%), 10 had macro metastasis (9.2%). Rates of pathological nodal negativity were significantly higher in patients with TN (100%) and HER2-positive tumors (97.1%) than in those with hormone-receptor-positive, HER2-negative tumors (63%) (p&lt; 0.001). Furthermore, a total of 41 (37.6%) patients had a complete pathologic response (pCR) of the primary breast tumor of which 40 (97.6%) had pathologically confirmed negative SLN and 1 (2.4%) had isolated tumor cells. A total of 67 patients had no pCR of which 48 (71.6%) had pathologically confirmed negative SLN and 19 (28.4%) were SLN positive (p &lt; 0.001). Rates of pCR were significantly higher in HER2-positive (70.6%) and TN tumors (47.6%) than in those with hormone-receptor-positive, HER2-negative tumors (13.0%) (p&lt; 0.001).
Conclusion
SLNB after NCT might be considered to be omitted in patients presenting with cN0 with TN and HER2+ tumors, as SLN is rarely positive. Furthermore, SLN was rarely found positive in patients who achieved pCR. However, more data are necessary for multivariate logistic regression and definite conclusions.
Citation Format: Beijert IJ, Francken A, Honkoop AH, Noorda EM. Sentinel lymph node biopsy after neoadjuvant chemo therapy in patients with clinically node negative breast cancer: Can sentinel lymph node biopsy be omitted in selected tumor subtypes? [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 P1-15-13.