RISK OF AXILLARY NODAL METASTASIS IN HER2-POSITIVE AND TRIPLE-NEGATIVE BREAST CANCER: EXPLORATION FOR OMISSION OF SENTINEL LYMPH NODE BIOPSY kiterius@snu.ac.kr

PW04-17

RISK OF AXILLARY NODAL METASTASIS IN HER2-POSITIVE AND TRIPLE-NEGATIVE BREAST CANCER: EXPLORATION FOR OMISSION OF SENTINEL LYMPH NODE BIOPSY

1

Korea (Republic of)

Poster Exhibition only

Recent trials, such as NAUTILUS, INSEMA, and SENOMAC investigated the oncological safety of omitting sentinel lymph node biopsy (SLNB). However, these studies included HER2-positive and triple-negative breast cancer (TNBC) in less than 10% of study populations, so axillary surgery de-escalation in these high-risk molecular subtypes still remains insufficient. This study aimed to investigate the rates of pN+ in HER2+ and TNBC patients with clinically node-negative disease, and explore the feasibility of SLNB omission in those subtypes.

We retrospectively reviewed the patients who underwent breast cancer surgery at a single institution between 2007 and 2023. Those who underwent mastectomy or had suspicious axillary lymph nodes on preoperative sonography were excluded.

A total of 555 patients were included, and HR+/HER2+, HR-/HER2+, and HR-/HER2- subtypes constituted 27.9%, 22.0%, and 50.1%, respectively. Among all, axillary node metastasis was identified in 45 patients (8.1%), while TNBC showed the lowest rate compared to other subtypes (4.7%, p=0.011). Multivariable logistic regression analysis demonstrated lymphovascular invasion (LVI) presence (Odds Ratio [OR] 4.13; 95% Confidence interval [CI] 2.15-7.91; p<0.001) and increasing tumor size (>1cm: OR 9.62, 95% CI 1.25-74.12, p=0.030; >2cm: OR 13.70, 95% CI 1.78-105.54, p=0.012) as independent predictors of nodal metastasis. Among the low-risk groups, defined as absent LVI and tumor size ≤1cm (n=102), only one patient (1.0%) had axillary node metastasis.

Our results demonstrate that aggressive subtypes including HER2-positive breast cancer and TNBC do not show high rates of pN+. In selected patients, omitting SLNB would be feasible, but multicenter, prospective studies are warranted.