P108. Opportunities for omission of axillary surgery after preoperative systemic therapy

Saturday, March 7, 2026

9:21 AM - 9:28 AM MST

Location: 301D

Primary Presenter(s)

TH

Tessa Higgins, MD (she/her/hers)

Dr.
Brigham and Womens Hospital
Boston, Massachusetts, United States

Slides

Co-Author(s)

Eliza H. Lorentzen, MD

Surgery Resident
Brigham and Womens Hospital
Boston, Massachusetts, United States
BZ

Biqi Zhang, MD

Brigham and Womens Hospital
Boston, Massachusetts, United States
Laura Dominici, MD

Associate Professor of Surgery
Harvard Medical School, Dana-Farber Cancer Institute, Beth Israel Deaconess Medical Center
Scituate, Massachusetts, United States
Ko Un Park, MD (she/her/hers)

Associate Surgeon
Brigham and Womens Hospital
Boston, Massachusetts, United States
TK

Tari King, MD

Emory University
Atlanta, Georgia, United States
Elizabeth A. Mittendorf, MD PhD MHCM (she/her/hers)

Professor of Surgery
Dana-Farber Cancer Institute
Boston, Massachusetts, United States
Elizabeth A. Mittendorf, MD PhD MHCM

Professor of Surgery
Dana-Farber Cancer Institute
Boston, Massachusetts, United States

Introduction: The SOUND and INSEMA trials demonstrated that in clinically node-negative (cN0) early-stage breast cancer patients undergoing upfront surgery, omission of sentinel lymph node biopsy (SLNB) is safe and does not compromise oncologic outcomes. This study was undertaken to determine if there is a population of cN0 breast cancer patients receving preoperative systemic therapy in whom SLNB could be omitted.

Methods: Patients receiving preoperative systemic therapy followed by surgery from January 2016 to August 2025 were identified in our institutional database. Clinicopathologic data including breast cancer subtype, presenting clinical stage, imaging performed at diagnosis, preoperative systemic therapy received, and pathologic stage were recorded.

Results:

Among 2393 patients receiving preoperative systemic therapy, 1083 were cN0; subtypes were: hormone receptor (HR)+/HER2- (n=215), HR+/HER2+ (n=301), HR-/HER2+ (n=144) and HR-/HER2- (n=423). The rates of pN0 disease were: 68.8% for HR+/HER2-, 85.0% for HR+/HER2+, 95.1% for HR-/HER2+ and 90.8% for HR-/HER2- disease. If pN0i+ disease was included, the rates were: 72.1% for HR+/HER2-, 88.0% for HR+/HER2+, 96.5% for HR-/HER2+ and 92.4% for HR-/HER2- disease. Limiting analyses to patients with a negative axillary ultrasound (AxUS) (or if suspicious, biopsy negative) at the time of diagnosis did not result in higher pN0 rates (table). For patients with HER2+ or triple negative breast cancer (TNBC), finding residual disease in the breast or axilla may inform adjuvant systemic therapy decisions. We therefore looked at the frequency of ypN+ disease in the setting of ypT0/is disease. This occurred in 10 (3.3%) patients with HR+/HER2+ disease, 2 (1.4%) patients with HR-/HER2+ disease and 1 (0.2%) patient with HR-/HER2- disease.

Conclusions: Patients with HR-negative disease receiving preoperative systemic therapy have ypN0/ypN0i+ rates >92%. In patients experiencing a complete response in the breast, missing nodal disease that would inform adjuvant therapy recommendations occurred in < 1.5%. These data support the two ongoing international trials evaluating omission of SLNB in patients with HER2+ or TNBC but question the studies’ requirement for AxUS and suggest that for HER2+ patients, outcomes be evaluated by HR status.

Learning Objectives:

Describe the rationale for omitting sentinel lymph node biopsy (SLNB) in selected patients with clinically node-negative breast cancer receiving preoperative systemic therapy.
Interpret patterns of nodal response across breast cancer subtypes following preoperative systemic therapy.
Evaluate ongoing and future clinical trials assessing the safety of omitting SLNB and identify patient populations most likely to benefit from de-escalated axillary management.