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Adding contrast-enhanced ultrasound markers to conventional axillary ultrasound improves specificity for predicting axillary lymph node metastasis in patients with breast cancer.

OBJECTIVE
To evaluate the diagnostic performance of contrast-enhanced ultrasound (CEUS) combined with conventional ultrasound (US) of axillary lymph nodes (ALNs) in predicting metastatic ALNs in patients with breast cancer.


METHODS
This retrospective study included 259 patients with breast cancer who underwent conventional US and CEUS. The parameters and patterns evaluated on conventional US included short axis diameter (S), long axis/short axis (L/S) ratio, cortical thickness, resistive index (RI), lymph node (LN) morphology of grey-scale US, hilum and vascular pattern. Meanwhile, enhancement pattern, wash-in time, time to peak (TP), maximum signal intensity, and duration of contrast enhancement were evaluated on CEUS. Univariate and multiple logistic regression analyses were performed to identify independent factors of ALN status. Three models (conventional US, CEUS, and combined parameters) were established. Receiver operating characteristic (ROC) curves were applied to evaluate the accuracy of the three predictive models.


RESULTS
On conventional axillary US, LN morphology and vascular pattern were independent factors in predicting metastatic ALNs. On CEUS, maximum signal intensity, duration of contrast enhancement, and TP were independent factors in predicting metastatic ALNs. When combining conventional US and CEUS features, five independent factors obtained from the conventional US and CEUS were associated with ALN status. ROC curve analysis showed that the use of CEUS markers combined with conventional US features (AUC = 0.965) was superior to the use of CEUS markers (AUC = 0.936) and conventional US features alone (AUC = 0.851).


CONCLUSION
Combining conventional US and CEUS features can enable discrimination of ALN status better than the use of CEUS and conventional US features alone.


ADVANCES IN KNOWLEDGE
The axillary lymph node status in breast cancer patients impacts the treatment decision. Our ultrasonic data demonstrated that CEUS features of ALNs in breast cancer patients could be image markers for predicting ALN status. Combining conventional US and CEUS features of ALNs can improve specificity discrimination of ALN status better than the use of CEUS and the conventional US features alone, which will help the treatment planning optimization.