FEASIBILITY OF SAVI SCOUT NON-WIRE LOCALIZATION OF AXILLARY LYMPH NODES Erica V. Bloomquist, MD Heather Wright, MD Department of Surgery - Breast Surgical Oncology Memorial Healthcare System Hollywood, FL Mary K. Hayes, MD Department of Radiology – Breast Imaging Sheridan Healthcare - Envision

Clinical Relevance: Biopsy and clip placement of abnormal lymph nodes (LN) documents extent of disease prior to treatment. Axillary findings (both biology and anatomic staging) inform therapy decisions. Targeted axillary dissection (TAD) via preoperative wires or radioactive seeds can supplement lymphoscintigraphy (SNL). SAVI SCOUT RADAR (SCOUT), an alternative non-wire, non-radioactive localization device deployed 0 - 30 days prior to surgery, can aid TAD.

Methods: Between July 2015 and September 2016, two experienced breast surgeons requested SCOUT localization to aid TAD in 16 patients aged 28 – 75. Axillary LN metastasis was previously confirmed by core needle biopsy with clip placement in 15/16 patients, and 14/16 received neoadjuvant chemotherapy (NACT). The radiologist used the SCOUT localization device 0 - 30 days prior to surgery in 16 patients with image guidance (11 Ultrasound, 3 Stereotactic, 2 CT) based on clipped LN visibility and patient body habitus.

US-Guided Localization for TAD with SCOUT was performed after NACT PATHOLOGY: 2.9 cm IDC ER+ PR- Her2 -, clear margins, LVI 0/2 SNL 1/1 Non-sentinel Scout TAD 14 mm Met LN

PET/CT Images of Biopsy proven Metastatic Left Axillary LN (clipped LN) PRE - Chemo POST - Chemo

CT-Guided Localization for TAD with SCOUT was performed after NACT SPECIMEN X Ray PATHOLOGY: 3 SNL and 0 non Sentinel LN excised 1/3 SNL with SCOUT TAD 6mm Met LN

POST – NACT Clipped LN was not visualized on US POST – NACT Clipped LN was not visualized on US. Stereotactic - Guided Localization for TAD with SCOUT was performed after NACT

POST-DEPLOY SCOUT LOCALIZATION and TAD SPECIMEN XRAY 0/3 SNL with SCOUT TAD PRE-DEPLOY (Pre-fire) Stereo Pair

Results: Radiologists successfully deployed and surgeons successfully excised the targeted (clipped) LN in 16/16 patients using SCOUT for supplementary TAD. Residual lymph node metastasis (2-22 mm size) was documented in 7 patients. SNL correctly identified the clipped (hot) LN with residual metastasis in 6/7 patients and supplementary TAD with SCOUT identified the clipped (hot and non-hot) LN with residual LN metastasis in all 7/7 patients.

Results: (continued) This preliminary finding suggests that SCOUT can aid TAD of the metastatic clipped (non-hot) non-sentinel LN. Our finding that 1/7 (14%) of the metastatic clipped LN did not correspond to the (hot) SNL is consistent with the ACOSOG Z1071 trial, where 11-20% SNL did not correspond to the documented metastatic LN at surgery.

Conclusions: SCOUT RADAR non-wire, non-radioactive localization device can be deployed 0-30 days prior to surgery for supplementary TAD in breast surgery patients, including those who have undergone neoadjuvant treatment for locally advanced breast cancer. Our institutional findings should be externally validated with a larger population.

References: Caudle et al. Feasibility trial for selective surgical localization of axillary lymph nodes containing metastases in breast cancer patients JAMA Surg. 2015 February ; 150(2): 137–143 doi:10.1001/jamasurg.2014.1086 Shin et al. Radiologic Mapping for Targeted Axillary Dissection: Needle Biopsy to Excision. AJR:207, December 2016