Axillary Nodal Upstaging in cT1N0 Invasive Lobular Carcinoma: Evaluating Applicability of SOUND Trial Results.

Authors

Thomas Amburn, Anita Mamtani, Jane J Chen, Varadan Sevilimedu, Sherry Shen, Komal Jhaveri, Monica Morrow

Published in

Annals of surgery. Sep 28, 2026. Epub Sep 28, 2026.

Abstract

To determine whether sentinel lymph node biopsy (SLNB) omission is applicable to stage 1 invasive lobular breast cancer (ILC).
The SOUND and INSEMA randomized controlled trials demonstrated that SLNB omission is noninferior to performing SLNB in early-stage, clinically node-negative (cT1-2N0), hormone receptor-positive/HER2-negative (HR+/HER2-) patients with breast cancer with negative preoperative axillary ultrasound. However, the applicability of SLNB omission in ILC has been uncertain.
We retrospectively identified patients with cT1N0, HR+/HER2- pure ILC, and normal axillary ultrasound who underwent upfront surgery with SLNB between 2009 and 2024. Clinicopathologic characteristics and pathologic nodal burden were evaluated.
Six hundred thirty-nine patients met the inclusion criteria, of whom the majority were postmenopausal women (72%) with low- to intermediate-grade (88%) and/or classic-type (84%) ILC. Axillary nodal metastases were identified on surgical pathology in 113 (17.7%) patients: 24 (3.8%) pN1mic, 74 (11.6%) pN1, 8 (1.2%) pN2, and 7 (1.1%) pN3. Node-positive patients were more often younger, premenopausal (36% vs. 26%, P=0.035), and presented with larger pathologic tumor size (46.7% vs. 18.3% pT2-3, P<0.001) and lymphovascular invasion (LVI) (19% vs. 3.2%, P<0.001). On univariate analysis, premenopausal status, high grade, and LVI were independently associated with nodal positivity. On multivariate analysis, only LVI remained independently associated with nodal positivity.
Among patients with SOUND-eligible ILC, 17.7% had axillary nodal metastasis and only 2.3% had extensive axillary nodal metastasis. These findings are comparable to the node-positive rates reported in the SLNB arm of the SOUND (13.7%) and INSEMA (15.1%) trials. High-risk features such as LVI and high grade were associated with nodal positivity.

PMID:
42802378
Bibliographic data and abstract were imported from PubMed on 28 Sep 2026.

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