ABSTRACT / SUMMARY Background: Breast cancer, the most common cancer in women, involves the axillary lymph nodes in 25-30% of cases. Treatment usually involves systemic therapy before surgery. Complete response to neoadjuvant systemic therapy (NST) with normalization of the lymph nodes translates to less extensive surgery, lower related morbidity, and sometimes less intense radiation therapy. To mark a positive lymph node, a biopsy marker is placed in the positive node pre-NST. Post-NST, the marked node is identified with ultrasound, mammography, or computed tomography to implant a localizer, which the surgeon uses for node removal. Ultrasound is the first- line imaging modality for this task. Still, the marker cannot be found sonographically in ~25% of cases, resulting in suboptimal or aborted localizations, delays to surgery, longer procedural times, increased patient discomfort or inconvenience, and increased absorbed costs by the clinical practice. Errors in identifying the proper node(s) may lead to false-negative results, over/undertreatment, and potential cancer recurrence. Marker migration remains another concern that can lead to misguided localization, directing the surgeon to the incorrect node. This research project aims to address these unmet and critical needs to develop reliable, readily ultrasound-conspicuous markers that are also resistant to migration. Methods: Our preliminary data suggest that physical features of markers, like surface roughness, can cause an ultrasound twinkling artifact or “twinkling signature” classically associated with kidney stones using color Doppler flow imaging. With the collective expertise of a diverse research team, we have developed markers using polymethyl methacrylate and additive manufacturing (three-dimensional printing). These markers generate robust twinkling signatures with ultrasound, are visible with multiple imaging modalities, and are resistant to marker migration. We will test the efficacy and safety of these markers in a porcine model over a six-month period to mimic the duration of NST treatment with chemotherapy. Lastly, we will conduct a Phase 1 clinical trial in breast cancer patients with our optimized marker to evaluate the long-term strength of the twinkling signature and the degree of marker migration. To accomplish the goals of this project, we propose these Specific Aims: Aim 1 Optimize ultrasound acquisition characteristics and the signal processing chain to robustly detect twinkling. Aim 2 Optimize physical characteristics of breast procedure markers that enhance Doppler-based twinkling and reduce marker migration. Aim 3 Assess long-term safety, twinkling persistence, and marker migration of candidate markers in a porcine animal model. Aim 4 Evaluate twinkling and migration of optimized markers in a Phase 1 clinical trial using markers implanted in a positive axillary lymph node prior to NST in patients with breast cancer.

NARRATIVE Breast cancer, the most common cancer in women, often metastasizes to nearby lymph nodes. A biopsy marker is placed in a metastatic lymph node for later ultrasound localization and surgical removal, but in a significant number of cases ultrasound detection of the marker can fail to locate the proper lymph node, so better markers are needed for improved treatment outcomes. Successful completion of this project will yield markers that 1) are conspicuous on ultrasound, and 2) do not migrate from the site of implantation.