Preoperative Axillary Ultrasound versus Sentinel Lymph Node Biopsy in Patients with Early Breast Cancer

Abstract

Background and objectives: With improved diagnostic means of early breast cancer, the percentage of cases with metastasis in axillary lymph nodes has decreased from 50%-75% to 15%-30%. Lymphadenectomy and sentinel lymph node biopsy are not treatment procedures, as they aim at axillary nodal staging in breast cancer. Being surgical interventions, they can lead to various complications. Therefore, recently much attention has been paid to the identification of non-invasive methods for axillary nodal staging. In many countries, ultrasound is a first-line method to evaluate axillary lymph node status. The aim of this study was to evaluate the prognostic value of ultrasound in detecting intact axillary lymph nodes and to assess the accuracy of ultrasound in detecting a heavy nodal disease burden. The additional objective was to evaluate patients' and tumor characteristics leading to false-negative results. Materials and Methods: A total of 227 women with newly diagnosed pT1 breast cancer were included to this prospective study conducted at the Breast Surgery Unit, Clinic of Surgery, Hospital of Lithuanian University of Health Sciences Kauno Klinikos, between May 1, 2016, and May 31, 2018. All patients underwent preoperative axillary ultrasound examination. Ultrasound data were compared with the results of histological examination. The accuracy and true-negative rate of ultrasound were calculated. The reasons of false-negative results were analyzed. Results: Of the 189 patients who had normally appearing axillary lymph nodes on preoperative ultrasound (PAUS-negative), 173 (91.5%) patients were also confirmed to have intact axillary lymph nodes (node-negative) by histological examination after surgery. The accuracy and the negative predictive value of ultrasound examination were 84.1% and 91.5%, respectively. In ≥3 node-positive cases, the accuracy and the negative predictive value increased to 88.7% and 98.3%, respectively. In total, false-negative results were found in 8.5% of the cases (n = 16); in the PAUS-negative group, false-negative results were recorded only in 1.6% of the cases (n = 3). The results of PAUS and pathological examination differed significantly between patients without and with lymphovascular invasion (LV0 vs. LV1, p < 0.001) as well as those showing no human epidermal growth factor receptor 2 (HER2) expression and patients with weakly or strongly expressed HER2 (HER2(0) vs. HER2(1), p = 0.024). Paired comparisons revealed that the true-negative rate was significantly different between the LV0 and LV1 groups (91% vs. 66.7%, p&nbsp;<&nbsp;0.05), and the false-negative rate was statistically significant different between the HER2(0) and HER2(1) groups (10.5% vs. 1.2%, p&nbsp;<&nbsp;0.05). Evaluation of other characteristics showed both the groups to be homogenous. Conclusions: Negative axillary ultrasound excluded axillary metastatic disease in 91.5% of the patients. PAUS had an accuracy of 88.7% in detecting a heavy nodal disease burden. With the absence of lymphovascular invasion (LV0), we can rely on PAUS examination that axillary lymph nodes are intact (PAUS-negative), and this patients' group could avoid sentinel lymph node biopsy. Patients without HER2 expression are at a greater likelihood of false-negative results; therefore, the findings of ultrasound that axillary lymph nodes are intact (PAUS-negative results) should be interpreted with caution.

Keywords: axillary lymph nodes; breast cancer; lymphadenectomy; sentinel lymph node biopsy; ultrasound.

Figure 1

Lymph node with normal appearance: (a) schematic drawing; (b) signs of preoperative axillary ultrasound-negative lymph node (oval shape, smooth cortex, unchanged, clearly visible fat gate); (c) central vascularity.

Figure 2

Suspicious lymph node: (a) schematic drawing; (b) signs of PAUS-positive lymph node (oval or rounded shape, local thickening of the cortex, dislocated gate); (c) mixed or peripheral vascularity.

Figure 3

Flowchart of involvement of axillary lymph nodes in 227 patients. PAUS, preoperative axillary ultrasound; SLN, sentinel lymph node; LMND, lymphadenectomy.

Figure 4

Flowchart of preoperative axillary ultrasound and histological examination findings in 227 patients. PAUS, preoperative axillary ultrasound.