Review of Variables Associated With Positive Surgical Margins Using Scout Reflector Localizations for Breast Conservation Therapy

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.

Cost-Effectiveness of Radar Localisation Versus Wire Localisation for Wide Local Excision of Non-palpable Breast Cancer

BACKGROUND

Wire localisation (WL) is the "gold standard" localisation technique for wide local excision (WLE) of non-palpable breast lesions but has disadvantages that have led to the development of wireless techniques. This study compared the cost-effectiveness of radar localisation (RL) to WL.

METHODS

This was a single-institution study of 110 prospective patients with early-stage breast cancer undergoing WLE using RL with the SCOUT® Surgical Guidance System (2021-2023) compared with a cohort of 110 patients using WL. Margin status, re-excision rates, and surgery delays associated with preoperative localisation were compared. Costs from a third-party payer perspective in Australian dollars (AUD$) calculated by using microcosting, break-even point, and cost-utility analyses.

RESULTS

A total of 110 WLEs using RL cost a total of AUD$402,281, in addition to the device cost of AUD$77,150. The average additional cost of a surgery delay was AUD$2318. Use of RL reduced the surgery delay rate by 10% (p = 0.029), preventing 11 delays with cost savings of AUD$25,496. No differences were identified in positive margin rates (RL: 11.8% vs. WL: 17.3%, p = 0.25) or re-excision rates (RL: 14.5% vs. WL: 21.8%, p = 0.221). In total, 290 RL cases are needed to break even. The cost of WLE using RL was greater than WL by AUD$567. There was a greater clinical benefit of 1.15 quality-adjusted life-years (QALYs) and an incremental cost-utility ratio of AUD$493 per QALY favouring RL.

CONCLUSIONS

Routine use of RL was a more cost-effective intervention than WL. Close to 300 RL cases are likely needed to be performed to recover costs of the medical device.

CLINICAL TRIAL REGISTRATION

ACTRN12624000068561.

Radar localization of breast and axillary lesions with SCOUT: a prospective single institution pilot study

BACKGROUND

Wire-guided localization has been the mainstay of localization techniques for non-palpable breast and axillary lesions prior to excision. Evidence is still growing for relatively newer localization technologies. This study evaluated the efficacy of the wireless localization technology, SCOUT®, for both breast and axillary surgery.

METHODS

Data were extracted from a prospective database (2021-2023) of consecutive patients undergoing wide local excision, excisional biopsy, targeted axillary dissection, or axillary lymph node dissection with SCOUT at a high-volume tertiary centre. Rates of successful reflector placement, intraoperative lesion localization, and reflector retrieval were evaluated. A survey of surgeon-reported ease of lesion localization and reflector retrieval was also evaluated.

CLINICAL TRIAL REGISTRATION

ACTRN386751.

RESULTS

One-hundred-ninety-five reflectors were deployed in 172 patients. Median interval between deployment and surgery was 3 days (range 1-20) and mean distance from reflector to lesion was 3.2 mm (standard deviation, SD 3.1). Rate of successful localization and reflector retrieval was 100% for both breast and axillary procedures. Mean operating time was 65.8 min (SD 33). None of the reflectors migrated. No reflector deployment or localization-related complications occurred. Ninety-eight percent of surgeons were satisfied with ease of localization for the first half of cases.

CONCLUSION

SCOUT is an accurate and reliable method to localize and excise both breast and axillary lesions, and it may overcome some of the limitations of wire-guided localization.

Comparison of Wire and Non-Wire Localisation Techniques in Breast Cancer Surgery: A Review of the Literature with Pooled Analysis

Background and Objectives: Wide local excision is a common procedure in the treatment of breast cancer. Wire-guided localisation (WGL) has been the gold standard for many years; however, several issues have been identified with this technique, and therefore, wire-free techniques have been developed. This scoping review synthesises the available literature comparing wire-guided localisation with the wire-free techniques used in breast-conserving cancer surgery. Materials and Methods: Multiple databases including Pubmed and MEDLINE were used to search articles between 1 January 2000 and 31 December 2022. Terms included "breast neoplasms", "margins of excision", and "reoperation". In total, 34/256 papers were selected for review. Comparisons were made between positive margins and re-excision rates of WGL with wire-free techniques including SAVI SCOUT, Magseed, ROLL, and RSL. Pooled p-values were calculated using chi-square testing to determine statistical significance. Results: Pooled analysis demonstrated statistically significant reductions in positive margins and re-excision rates when SAVI SCOUT, RSL, and ROLL were compared with WGL. When SAVI SCOUT was compared to WGL, there were fewer re-excisions {(8.6% vs. 18.8%; p = 0.0001) and positive margins (10.6% vs. 15.0%; p = 0.0105)}, respectively. This was also the case in the ROLL and RSL groups. When compared to WGL; lower re-excision rates and positive margins were noted {(12.6% vs. 20.8%; p = 0.0007), (17.0% vs. 22.9%; p = 0.0268)} for ROLL and for RSL, respectively {(6.8% vs. 14.9%),(12.36% vs. 21.4%) (p = 0.0001)}. Magseed localisation demonstrated lower rates of re-excision than WGL (13.44% vs. 15.42%; p = 0.0534), but the results were not statistically significant. Conclusions: SAVI SCOUT, Magseed, ROLL, and RSL techniques were reviewed. Pooled analysis indicates wire-free techniques, specifically SAVI SCOUT, ROLL, and RSL, provide statistically significant reductions in re-excision rates and positive margin rates compared to WGL. However, additional studies and systematic analysis are required to ascertain superiority between techniques.

Fluoroscopic Intraoperative Breast Neoplasm and Node Detection

BACKGROUND

Preoperative localization is necessary for nonpalpable breast lesions. A novel procedure, fluoroscopic intraoperative neoplasm and node detection (FIND), obviates the preoperative painful and potentially expensive localization by using intraoperative visualization of the standard clip placed during diagnostic biopsy. We hypothesized FIND would improve negative margin rates.

STUDY DESIGN

This is an IRB-approved retrospective study (September 2016 to March 2021). Electronic chart review identified breast and axillary node procedures using wire localization (WL) or FIND. Primary outcome was margin status. Secondary outcomes included re-excision rate, specimen weight, surgery time, and axillary node localization rate.

RESULTS

We identified 459 patients, of whom 116 (25.3%) underwent FIND and 343 (74.7%) WL. Of these, 68.1% of FIND and 72.0% of WL procedures were for malignant lesions. Final margin positivity was 5.1% (4 of 79) for FIND and 16.6% (41 of 247) for WL (p = 0.008). This difference lost statistical significance on multivariable logistic regression (p = 0.652). Re-excision rates were 7.6% and 14.6% for FIND and WL (p = 0.125), with an equivalent mean specimen weight (p = 0.502), and mean surgery time of 177.5 ± 81.7 and 157.1 ± 66.8 minutes, respectively (mean ± SD; p = 0.022). FIND identified all (29 of 29) targeted axillary nodes, and WL identified only 80.1% (21 of 26) (p = 0.019).

CONCLUSIONS

FIND has lower positive margin rates and a trend towards lower re-excision rates compared with WL, proving its value in localizing nonpalpable breast lesions. It also offers accurate localization of axillary nodes, valuable in the era of targeted axillary dissection. It is a method of visual localization, using a skill and equipment surgeons already have, and saves patients and medical systems an additional schedule-disruptive, painful procedure, especially valuable when using novel localization devices is cost-prohibitive.