P10. Is routine intraoperative sentinel lymph node frozen section necessary in clinically node-negative patients treated with neoadjuvant chemotherapy?

Thursday, March 5, 2026

11:35 AM - 11:42 AM MST

Location: 301A

Primary Presenter(s)

TT

Tara Talaie, MD, MS

Breast Service, Department of Surgery
Memorial Sloan Kettering Cancer Center
New York, New York, United States

Co-Author(s)

VS

Varadan Sevilimedu, MBBS, DrPH

Biostatistics Service, Department of Epidemiology and Biostatistics
Memorial Sloan Kettering Cancer Center
New York, New York, United States
CS

Christopher Schwartz, DO

Department of Pathology and Laboratory Medicine
Memorial Sloan Kettering Cancer Center
New York, New York, United States
Andrea V. Barrio, MD

Breast Service, Department of Surgery
Memorial Sloan Kettering Cancer Center
New York, New York, United States
Monica Morrow, MD (she/her/hers)

Chief, Breast Service, Department of Surgery; Anne Burnett Windfohr Chair of Clinical Oncology; Vice President, Women in Science and Medicine, MSKCC; Professor of Surgery, Weill Cornell Medical College of Cornell University
Memorial Sloan Kettering Cancer Center
New York, New York, United States
Giacomo Montagna, MD, MPH

Breast Service, Department of Surgery
Memorial Sloan Kettering Cancer Center
New York, New York, United States

Introduction: There is mounting evidence that axillary lymph node dissection (ALND) does not provide oncologic benefit in patients with low-volume nodal disease (isolated tumor cells [ITCs] and micrometastases) after neoadjuvant chemotherapy (NAC). The rate of nodal metastases (ypN+) in cN0 patients who undergo NAC is low (3-27%), and about half have low-volume disease. We evaluated the utility of intraoperative sentinel lymph node (SLN) frozen section (FS) by subtype in cN0 patients treated with NAC.

Methods: Consecutive cT1-3N0 breast cancer patients treated with NAC followed by surgery between 1/2014-12/2021 were identified. Clinical nodal status was determined by physical exam. If axillary imaging was performed, patients with indeterminate lymph nodes were included if lymph node biopsy was negative or if second-look imaging was normal. Clinicopathological factors were compared between ypN0 and ypN+. Multivariable logistic regression (MVR) was used to identify preoperative factors associated with ypN status. The SLN FS false-negative rate (FNR) was calculated using the total negative FS result as the denominator.

Results: Of 718 cN0 patients, only 69 (9.6%) were ypN+ on final pathology. Median age was 50 years; the majority of patients had cT2 (median size 3 cm), ductal (95%), and HER2+ (44%) or 38% triple negative (TN) tumors. The rate of ypN+ varied significantly by subtype: HR+/HER2- 18%, HR+/HER2+ 10.6%, HR-/HER2+ 3.8%, and TN 6.6% (Table). On MVR, cT3 tumors (Ref [cT1]: OR 3.11, 95% CI 1.00-9.63) and lobular histology (Ref [ductal] OR 5.26, 95% CI 2.17-12.8) were independently associated with ypN+, while TN subtype (Ref [HR+/HER2-] OR 0.43, 95% CI 0.20-0.93) and radiological complete response (cCR) on MRI (Ref [non cCR] OR 0.24, 95% CI 0.08-0.69) were independently associated with ypN0. FS diagnosis was deferred in 0.2% (n = 2). Of the 652 negative FS cases, 3 were ypN+ on permanent H&E (FNR 0.5%); all had low-volume disease. Of 69 ypN+ patients, 33 (48%) had low-volume disease (n = 10 [15%] ITCS, n = 23 (33%) micrometastases). The overall rate of residual macrometastases was 5% (n = 36), but varied by subtype (HR+/HER2- [11%], HR+/HER2+ [5.5%], HR-/HER2+ [2.5%], and TN [4%]).

Conclusions: If FS had been omitted in this cohort of cN0 patients treated with NAC, only 5% (n = 36) of patients with residual macrometastases would have required return to the operating room for completion ALND. Our findings suggest that routine use of FS could be eliminated, especially in patients with HR-/HER2+ and TN tumors.

Learning Objectives:

Understand the rate of ypN+ among cN0 patients completing NAC, and what factors are associated with ypN+.
Identify the proportion of ITCs vs micrometastases and macrometastases among ypN+ patients.
Integrate these results with recent data indicating no benefit of ALND in patients with low-volume nodal disease after NAC.