Savi-Scout Radar Localization: Transitioning From the Traditional Wire Localization to Wireless Technology for Surgical Guidance at Lumpectomies

Innovations in the localization techniques for non-palpable breast lesions: Make invisible visible

Non-palpable breast cancer lesions pose a challenge for surgeons to resect cancer lesions. Making 'invisible' lesions 'visible' is the main strategy. Currently, multiple preoperative localization techniques have been applied in clinical. Among them, wire-guided localization (WGL) is the most common procedure due to its convenience and low cost. However, its limitations including discomfort, wire migration and the coupling of localization and operation procedures cause troubles for surgeons and patients. The desire for localization methods improvement, accompanied by the advance of emerging science and technology, leads to the development of a series of locating approaches for breast non-palpable lesions, aiming to improve locating accuracy while reducing adverse events. These emerging methods have undergone improvements from steel wire to functional particles, from radioactivity to non-radioactive, which help doctors and patients choose a more appropriate scheme. This review outlines the principles, procedures, advantages and disadvantages of these locating methods, and highlights the latest progress and related clinical data on innovative locating approaches. Finally, we briefly discuss the current challenges and future opportunities for the clinical application of these localization approaches.

Localization procedure for breast lesions at time of biopsy - Which patients would benefit?

BACKGROUND

The diagnosis and treatment of non-palpable breast lesions is a multistep pathway that can involve imaging, tissue biopsy, clip placement, localization, and surgical resection. To minimize the procedural burden on patients, placement of localization seeds at time of initial biopsy has been considered. However, benefit to this patient population remains unclear. This study, therefore, aimed to determine the number of patients within our own institution that may benefit from upfront localization and characterize an appropriate target population.

METHODS

A single institution retrospective cross-sectional study was conducted with assessment of all patients who underwent core needle biopsy (CNB) and/or breast cancer surgery at a regional high-volume breast centre between January 1 and December 31, 2018. Patients who underwent CNB with a subsequent radiological localization procedure and breast cancer surgeries that utilized localization were evaluated in order to model seed use.

RESULTS

In total, 314 CNB and 634 breast cancer surgeries were performed. Within the CNB cohort, 60 (19.1 ​%) required localization. Of the breast cancer surgeries performed, 420 (66.2 ​%) were breast-conserving surgery and 303 (47.8 ​%) required localization.

CONCLUSION

With some localization technologies, the localization procedure can be coupled with biopsy and eliminate the need for a clip as the length of implantation is unrestricted. That said, our institutional data suggests that only a small portion of patients undergoing breast biopsy would benefit from upfront localization and a minority of breast cancer surgeries require localization. Further characterization of this specific patient population is needed to streamline management pathways.

SCOUT® Localization Using MRI Guidance: Initial Experience

OBJECTIVE

The Food and Drug Administration approved the MRI-compatible wireless SCOUT localization system in April 2022. The purpose of this study was to evaluate feasibility of SCOUT localization under MRI guidance. We present our initial experience adopting MRI-guided SCOUT localization and compare it to MRI-guided wire localization.

METHODS

Electronic medical records and imaging were retrospectively reviewed for all patients who underwent MRI-guided SCOUT or wire localization at our institution between October 2022 and July 2023. Statistical analysis was performed using 2-sample proportion and Wilcoxon rank-sum tests.

RESULTS

There were 14 MRI-guided SCOUT and 23 MRI-guided wire localization cases during the study period. All SCOUTs were placed without complication and were considered to be in adequate proximity to the target. There was no significant difference in complication rate (P = .25) or days lapsed from MRI-detected abnormality to surgery (P = .82) between SCOUT and wire cases. SCOUT was placed at time of biopsy for 71% (10/14) of cases. 57% (8/14) of SCOUT cases were used for breast conservation surgery (BCS) compared to 100% (23/23) of wire cases (P <.01), with all 6 SCOUTs not used for BCS placed at time of biopsy.

CONCLUSION

MRI-guided SCOUT localization is feasible and offers an alternative to MRI-guided wire localization, with no SCOUT complications reported. SCOUT placement at time of biopsy obviates the need for an additional procedure, but predicting appropriateness is challenging, with 60% (6/10) of SCOUTs placed at time of MRI-guided biopsy not used for subsequent localization surgery.

SCOUT® Radar Localization at Time of Breast Biopsy

OBJECTIVE

Evaluate surgical utilization of SCOUT reflectors placed at breast biopsy.

METHODS

Consent was waived for this retrospective IRB-approved, HIPAA-compliant study. Breast biopsy examinations that reported the term "SCOUT" between January 2021 and June 2022 were identified using an institutional search engine. Cases were included if a SCOUT reflector was placed at time of breast biopsy and excluded if lesion pathology was already known. Analysis was performed at the lesion level. A multivariate-regression analysis evaluated 6 variables with potential impact on SCOUT utilization.

RESULTS

One hundred twenty-one lesions in 112 patients met inclusion criteria. Biopsy yielded 93% (113/121) malignant, 3% (4/121) elevated risk, 2% (2/121) benign-discordant, and 2% (2/121) benign-concordant results. Two cases lost to follow-up were excluded. SCOUT reflectors were utilized for lumpectomy (58%, 69/119 lesions) and excisional biopsy (6%, 7/119 lesions). SCOUTs were not utilized due to mastectomy (23%, 27/119), subsequent wire localization (2%, 2/119), and nonsurgical cases (12%, 14/119). Reflector placement utilization was 52% higher for findings less than 3.5 cm in size (P <.001), 33% higher in patients without prior treated breast cancer (P = .012), and 19% higher in patients with no suspicious ipsilateral lymph node (P = .048).

CONCLUSION

SCOUT reflector placement at time of biopsy was utilized for surgery 64% (76/119) of the time, although most (98%, 119/121) biopsies were malignant, elevated risk, or benign-discordant. Factors increasing reflector utilization include smaller lesion size, no suspicious ipsilateral lymph node, and no prior treated breast cancer.

Use of the lateral arm in tomosynthesis-guided SCOUT Reflector placement procedures

Preoperative localization procedures are important for guiding surgical excision of non-palpable findings in the breast. The SCOUT Reflector (Merit Medical, South Jordan UT, USA) is a non-wire-based localization device that has been incorporated into clinical use with great success. SCOUT Reflectors can be placed using several imaging modalities, including tomosynthesis. One drawback to SCOUT Reflector placement under tomosynthesis guidance is an inability to directly visualize the introducer needle tip, a factor that limits precision. In this brief communication, we describe the use of a lateral arm attachment for tomosynthesis guided SCOUT Reflector placement. Precise SCOUT Reflector placement can be achieved using the lateral arm due to the ability to clearly visualize the introducer needle and the SCOUT Reflector within the introducer needle bore prior to deployment.