Abstract P1-01-11: Axillary extensive burden evaluation by ultrasound in preoperative nodal staging in breast cancer patients
Authors: Defoort Camille , Chemaly Joanna , Ceugnart Luc , Chauvet Marie-Pierre 
Published: March 2022

Purpose :Since ACOSOG Z1011 trial, the role of axillary US preoperative has been redirected for predicting extensive axillary involvement. Our study is aimed to evaluate routinely US axillary prediction for extensive nodal burden in breast cancer. Materials and methods :The study was approved by the institutional reaview board and the requirement for in-formed consent was waived.All patients in our institution with early-stage invasive breast cancer have a systematic axillary ultrasound (US) evaluation before surgery.A prospective study of radiology and pathology records concerns all consecutives patients to evaluate US correlation with surgical findings beetwen November 1, 2020 and July 15, 2021.Neoadjuvant chemotherapy, ductal carcinoma in situ on breast biopsy, and relapse cases were excluded.Criteria used to define abnormal lymph nodes included : focal or diffuse cortical thickening with cortex thicker than &gt;4mm, replacement or effacement of the fatty hilium, or rounder lymph node.3 US prediction groups were defined as: US G0 normal (no suspicious lymph node) ;US G1 non extensive involvement (1 or 2 suspicious nodes) ; US G2 extensive involvement (≥3 suspicious nodes).In case of preoperative positive axillary biopsy, positive intraoperative examination, or patients without Acosog criteria, an axillary dissection was systematically performed.3 pathologic groups were defined as : path G0 (pN0) ; path G1 (≤2pN+) ; path G2 (≥3pN+).Statiscal analysis was performed with the chi-square the Fisher’s exact test.NPV for extensive axillary burden is defined as the proportion of patients with a negative test result (US G0 or US G1) that does not have extensive nodal involvement histologically (path G0 or path G1). Results. The study is still ongoing. On the 241 first cases, 64.3% (155/241) were cT1, 82.9% (200/241) were cN0. 163(78.3%) had Ductal invasive carcinoma, 37 were lobular histologic characteristics (17.8%) and 8 were mixted (3.8%).6.2% (15/241) patients presented extensive nodal involvement.

ConclusionThe results of this study are preliminary. They will be completed after the next study closure. In the first results, it is globally observed that the preoperative ultrasound makes it possible to exclude more than 97% of extensive involvement (&gt;2pN+). In case of less than 3 US suspected axillary nodes , sentinel node biospy remains indicated. The false negative rate cannot be calculated on this day and will not be presented until later.

Path G0Path G1Path G2totalUS G0156243187US G1310922US G20033total1593415241VPN for extensive nodal disease is 97.9% (193/197).In abnormal US groups (US G1+US G2), 48% (12/24) patients had extensive axillary involvement.

Citation Format: Camille Defoort, Joanna Chemaly, Luc Ceugnart, Marie-Pierre Chauvet. Axillary extensive burden evaluation by ultrasound in preoperative nodal staging in breast cancer patients [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-01-11.