Ultrasound-Visible 3D Nickel-Titanium Clip for Tumor Localization After Neoadjuvant Therapy in Early Breast Cancer: A...

Background: Neoadjuvant systemic therapy (NST) enables tumor downsizing and increases the feasibility of breast-conserving surgery (BCS) in patients with early breast cancer (EBC). Reliable tumor localization after NST remains challenging, particularly in patients with a complete clinical response. If clips are not visible on ultrasound, stereotactic mammography-guided wire localization is required, which involves additional radiation exposure and may increase patient discomfort and procedural complexity. The 3D-shaped Tumark^® Vision clip may enable ultrasound-guided localization after NST. Methods: In this prospective multicenter registry study (NCT04468113), 324 patients with biopsy-proven EBC scheduled for NST and breast-conserving surgery were enrolled across 19 German centers. Clip placement was performed under ultrasound guidance prior to NST, and clip detectability was assessed at predefined time points during therapy (4-8, 9-12, and ≥13 weeks after treatment initiation). Detection rates, visualization, and preoperative localization methods were recorded. Non-detectable clips required stereotactic wire localization, whereas ultrasound-guided localization was performed for detectable clips. Results: The preoperative detection rate was 91.1%. Clip detectability was higher in patients with longer NST durations and partial response by imaging. Ultrasound-guided wire localization was feasible in 214 patients (83.9%); among these, 165 patients (64.7%) underwent localization without and 49 patients (19.2%) with post-procedural mammographic verification. Stereotactic localization was required in 41 patients (16.1%), primarily due to non-visualization of the clip on ultrasound. The accuracy of ultrasound for residual tumor assessment was moderate (72.0%), with a sensitivity of 70.7%, indicating limitations in its ability to reliably assess residual tumor extent as a standalone modality. Conclusions: The 3D nickel-titanium clip enables ultrasound-guided tumor localization after NST in the majority of patients with early breast cancer, although additional mammographic guidance remains necessary in a relevant proportion of cases.