Contrast-enhanced lymphatic US can improve the preoperative diagnostic performance for sentinel lymph nodes in early breast cancer

Abstract

Objectives: To evaluate the preoperative diagnostic value of contrast-enhanced lymphatic ultrasound (CEUS) for the sentinel lymph node (SLN) status in early breast cancer.

Materials and methods: We prospectively recruited 102 consecutive patients with clinically node-negative early breast cancer from July 2021 to October 2021. All patients underwent conventional US and percutaneous CEUS examinations. The CEUS of SLNs were classified into four enhancement patterns: homogeneous (I), featured inhomogeneous (II), focal defect (III), and no enhancement (IV). The diagnostic performance of conventional US and CEUS for SLN metastasis was assessed by receiver operating characteristic (ROC) curves and decision curves.

Results: A total of 78 women were enrolled in this study, including 55, 18, and 5 patients with negative axilla, 1-2, and ≥ 3 metastastic SLNs pathologically, respectively. The identification rate of SLNs by CEUS was 100%. Patterns I and II can select 91.7% (44/48) of patients with disease-free axilla, while patterns III and IV had higher percentages of metastasis (65.2%, p < 0.001 and 57.1%, p < 0.002, respectively). For the SLN metastatic burden, 100% (48/48) of patients with pattern I/II had ≤ 2 metastatic SLNs. Compared with conventional US, the CEUS enhancement patterns showed significant improvement in diagnosing metastatic SLNs (0.813 vs 0.601, p < 0.001). CEUS had greater clinical benefits and correctly reclassified 48% of metastatic SLNs (p < 0.001) without sacrificing the classification accuracy of negative SLNs (p = 0.25), and could improve prediction accuracy by 0.42 (p < 0.001).

Conclusions: CEUS demonstrated better diagnostic performance and greater clinical benefits than conventional US for the preoperative diagnosis of SLNs, showing its potential to select candidates for precluding axillary surgery in early breast cancer.

Key points: • The homogeneous and featured inhomogeneous enhancement of SLNs are highly suggestive of negative LNs, while focal defect (p < 0.001) and no enhancement (p < 0.002) patterns had higher percentages of metastasis. • The proportion of SLNs with highly suspicious signs on conventional US increases as the type of enhancement pattern increases (no suspicious signs in pattern I/II, 34.8% in pattern III, and 85.7% in pattern IV). • Compared with conventional US, CEUS improved the area under the receiver operating characteristic curve (0.813 vs. 0.601, p < 0.001) and had greater clinical benefits (IDI = 0.42, p < 0.001) for the diagnosis of axillary metastasis.

Keywords: Breast neoplasms; Contrast media; Sentinel lymph node; Ultrasonography.

Fig. 1

Flowchart of this study. CEUS, contrast-enhanced US; US, ultrasound; SLN, sentinel lymph node

Fig. 2

The four types of CEUS enhancement patterns of SLNs. With the live-dual mode, the enhancement pattern (left) and the greyscale (right) images are shown in figures. A Pattern I, homogeneous enhancement. The entire lymph node showed bright, homogeneous enhancement. B Pattern II, cribriform enhancement. The SLN had a low enhancement with an even distribution inside the node resembling a sieve mesh. C Pattern II, half-moon enhancement, a semilunar, homogeneous enhancement with a centred afferent lymph vessel or enhancement of the cortex with a contrast agent. D Pattern II, ring enhancement, a regular, uniform, bright ring enhancement at the periphery of the node. E Pattern III, focal defect enhancement. The uneven distribution of the contrast agent with filling defect areas (*) of the SLN is seen correlating to the focal eccentric cortical thickening (arrow) on grayscale US. F Pattern IV, no enhancement. The SLN showed no enhancement in the whole region (*) and focal eccentric cortical thickening (arrow) on grayscale US. US, ultrasound; CEUS, contrast-enhanced lymphatic US; SLN, sentinel lymph node

Fig. 3

The CEUS and conventional US for diagnosis of metastatic SLNs. a The receiver operating characteristic (ROC) curves of conventional US (blue line) and CEUS enhancement pattern (red line). b Decision curves of conventional US (blue line) and CEUS enhancement pattern (red line) for metastatic SLNs. US, ultrasound; CEUS, contrast-enhanced lymphatic US; SLN, sentinel lymph node; ROC, the receiver operating characteristic