A novel approach to identify sentinel lymph nodes using microbubbles and contrast enhanced ultrasound in preoperative breast cancer patients

Abstract

e11543 Background: In patients with early invasive breast cancer, surgical excision of sentinel lymph nodes (SLN) has been shown to be a safe and accurate first-line technique to stage the axilla. In animal models, superficial lymphatics can be imaged using ultrasound and intradermal microbubbles. We investigated the ability of contrast enhanced ultrasound to identify SLN preoperatively in breast cancer patients. Methods: We recruited 46 consecutive consenting patients with primary breast cancer. Pre-operatively; patients received periareolar intra-dermal injection of microbubble contrast agent, breast lymphatics were visualised by ultrasound and followed to identify putative axillary SLN. In 41 patients, we aimed to place guide-wires in the SLN. Patients then underwent standard operative tumour excision, SLN biopsy and histopathological analysis. Results: Microbubble enhancement identified putative SLN in 5 successive patients. In 36 patients, putative SLN were visualised and guide-wires deployed. Operative findings confirmed the wired lymph nodes (LN) were SLN. In 2 cases, SLN contrast enhancement failed but guide-wires were placed into prominent grey-scale imaged LN. These wired LN were not SLN. In 3 patients, the procedure failed. Contrast enhanced ultrasound correctly identified SLN in 36 of 41 patients (88%). Five patients were found to have metastasis. In all metastatic cases, SLN were correctly identified and localised with guide-wires pre-operatively. Conclusions: Microbubbles readily enter breast lymphatics and contrast enhanced ultrasound may represent a practical method to identify SLN. Improvements in percutaneous techniques may facilitate ultrasound guided SLN excision in the breast clinic and could reduce the numbers of patients requiring axillary surgery. No significant financial relationships to disclose.