Breast MRI in patients after breast conserving surgery with sentinel node procedure using a superparamagnetic tracer

Impact of low dose superparamagnetic iron oxide tracer for sentinel node biopsy in breast conserving treatment on susceptibility artefacts on magnetic resonance imaging and contrast enhanced mammography

BACKGROUND

Residual particles of superparamagnetic iron oxide (SPIO) tracer, used for sentinel node biopsy, cause susceptibility artefacts on breast Magnetic Resonance Imaging (MRI). We investigated the impact of these artefacts on the imaging quality of MRI and explored whether contrast-enhanced mammography (CEM) could be an alternative in the follow-up of breast cancer patients.

MATERIALS AND METHODS

Data on patients' characteristics, injection site, presence, size (mm) of artefacts on full-field digital mammography (FFDM)/CEM, MRI after 1 ml SPIO was recorded. Image quality scored by two breast radiologists using a 4-point Likert system: 0: no artefacts 1: good diagnostic quality 2: impaired but still readable 3: hampered clinical assessment. Continuous variables reported as means and standard deviations (SD), categorical variables as count and percentage.

RESULTS

On FFDM/CEM, performed 13 months postoperatively, no iron SPIO particles were detected, with a Likert score of 0. In all MRI (100%) images, executed at 16.6 months after SPIO injection, susceptibility artefacts at the injection sites i.e., retroareolair and lateral quadrant were observed with a mean size of 41.9 ± 9.8 mm (SD) by observer 1, and 44.8 ± 12.5 mm (SD) by observer 2, independent of the injection site. Both observers scored a Likert score of 2: locally impaired on all MRI images and sequences.

CONCLUSIONS

Even 1 ml SPIO tracer used for sentinel node procedure impairs the evaluation of breast MRI at the tracer injection site beyond one year of follow-up. No impairment was observed on FFDM/CEM, suggesting that CEM might be a reliable alternative to breast MRI if required.

Avoiding unnecessary sentinel lymph node biopsy with the use of superparamagnetic iron oxide mapping agents (Magtrace®) in breast surgery

BACKGROUND

Superparamagnetic iron oxide (SPIO) (Magtrace®) is a non-radioactive liquid tracer that can stay in the sentinel lymph nodes for 30 days. Injection of SPIO at time of primary breast surgery where upfront sentinel lymph node biopsy (SLNB) is not immediately indicated allows for a return to theatre if pathology then identifies invasive disease. SLNB is associated with paraesthesia, pain, seroma formation and lymphoedema risk. Hence, our study aims to assess the use of SPIO to avoid upfront SLNB in breast surgery for ductal carcinoma in situ (DCIS) and prophylaxis.

METHODS

Retrospective single-centre study of consecutive patients who underwent injection of SPIO tracer at time of primary breast surgery to avoid upfront SLNB at Chris O'Brien Lifehouse, Sydney, NSW, Australia over a 10-month period.

RESULTS

SPIO was injected 38 times, with 34 at time of mastectomy and four cases at time of wide local excision. The indication for surgery was DCIS in 18 cases, risk reduction in 17 cases and other indications in three patients. Six cases (15.8%) required delayed SLNB (D-SLNB) due to the finding of invasive disease on post-operative histopathology. All patients who underwent D-SLNB had nodes successfully localized with SPIO.

CONCLUSION

In our cohort, 84.2% of cases were able to avoid upfront SLNB, and hence avoid the associated complications of SLNB. SPIO injection was successful in localizing the SLN in all cases at time of surgery for D-SLNB. This technique was safe with few associated complications.

Magnetic Seed vs Guidewire Breast Cancer Localization With Magnetic Lymph Node Detection: A Randomized Clinical Trial

Importance

Guidewires have been the standard for breast lesion localization but pose operative and logistic challenges. Paramagnetic seeds have shown promising results, but to the authors' knowledge, no randomized comparison has been performed.

Objective

To determine whether the combination of a paramagnetic seed and superparamagnetic iron oxide (SPIO) is equivalent to guidewire and SPIO for breast cancer localization and sentinel lymph node detection (SLND).

Design, Setting, and Participants

This was a phase 3, pragmatic, equivalence, 2-arm, open-label, randomized clinical trial conducted at 3 university and/or community hospitals in Sweden from May 2018 to May 2022. Included in the study were patients with early breast cancer planned for breast conservation and SLND. Study data were analyzed July to November 2022.

Interventions

Participants were randomly assigned 1:1 to a paramagnetic seed or a guidewire. All patients underwent SLND with SPIO.

Main Outcomes and Measures

Re-excision rate and resection ratio (defined as actual resection volume / optimal resection volume).

Results

A total of 426 women (median [IQR] age, 65 [56-71] years; median [IQR] tumor size, 11 [8-15] mm) were included in the study. The re-excision rate was 2.90% (95% CI, 1.60%-4.80%), and the median (IQR) resection ratio was 1.96 (1.15-3.44). No differences were found between the guidewire and the seed in re-excisions (6 of 211 [2.84%] vs 6 of 209 [2.87%]; difference, -0.03%; 95% CI, -3.20% to 3.20%; P = .99) or resection ratio (median, 1.93; IQR, 1.18-3.43 vs median, 2.01; IQR, 1.11-3.47; P = .70). Overall SLN detection was 98.6% (95% CI, 97.1%-99.4%) with no differences between arms (203 of 207 [98.1%] vs 204 of 206 [99.0%]; difference, -0.9%; 95% CI, -3.6% to 1.8%; P = .72). More failed localizations occurred with the guidewire (21 of 208 [10.1%] vs 4 of 215 [1.9%]; difference, 8.2%; 95% CI, 3.3%-13.2%; P < .001). Median (IQR) time to specimen excision was shorter for the seed (15 [10-22] minutes vs 18 [12-30] minutes; P = .01), as was the total operative time (69 [56-86] minutes vs 75.5 [59-101] minutes; P = .03). The experience of surgeons, radiologists, and surgical coordinators was better with the seed.

Conclusions and Relevance

The combination of SPIO and a paramagnetic seed performed comparably with SPIO and guidewire for breast cancer conserving surgery and resulted in more successful localizations, shorter operative times, and better experience.

Trial Registration

ISRCTN.org Identifier: ISRCTN11914537.

How to 19F MRI: applications, technique, and getting started

Magnetic resonance imaging (MRI) plays a significant role in the routine imaging workflow, providing both anatomical and functional information. 19F MRI is an evolving imaging modality where instead of 1H, 19F nuclei are excited. As the signal from endogenous 19F in the body is negligible, exogenous 19F signals obtained by 19F radiofrequency coils are exceptionally specific. Highly fluorinated agents targeting particular biological processes (i.e., the presence of immune cells) have been visualised using 19F MRI, highlighting its potential for non-invasive and longitudinal molecular imaging. This article aims to provide both a broad overview of the various applications of 19F MRI, with cancer imaging as a focus, as well as a practical guide to 19F imaging. We will discuss the essential elements of a 19F system and address common pitfalls during acquisition. Last but not least, we will highlight future perspectives that will enhance the role of this modality. While not an exhaustive exploration of all 19F literature, we endeavour to encapsulate the broad themes of the field and introduce the world of 19F molecular imaging to newcomers. 19F MRI bridges several domains, imaging, physics, chemistry, and biology, necessitating multidisciplinary teams to be able to harness this technology effectively. As further technical developments allow for greater sensitivity, we envision that 19F MRI can help unlock insight into biological processes non-invasively and longitudinally.

The Magnetic Technique-A Novel and Promising Method to Improve Axillary Staging Localisation from a Swedish Perspective

The magnetic technique using superparamagnetic nanoparticles of iron oxide has been well established for sentinel lymph node detection. Its main advantage is in the context of logistics, with the possibility to inject several weeks before surgery and the possibility to give access to sentinel lymph node biopsy for women worldwide in places without nuclear medicine facilities. We have not yet seen the full potential of this technique, and new implications have been developed for breast tumour localisation with paramagnetic clips and axillary staging after neoadjuvant chemotherapy using paramagnetic clips inserted in lymph node metastases before chemotherapy. In this report, we have presented our experience of the magnetic technique starting in 2014, and we have highlighted our current and future research directions.

Sentinel Lymph Node Detection in Breast Cancer: An Innovative Technique

(1) Background: Sentinel lymph node biopsy is important in the search for metastases, especially in patients with malignant breast disease. Our study proposed new techniques to prevent complications such as possible postoperative seroma formation, pain or hypoesthesia of the axillary cord and medial arm surface, as well as motor deficits, to avoid disabling outcomes and presents initial data from our experience with the sentinel lymph node biopsy technique. (2) Methods: We mainly used two radioactive tracer detection techniques and a new technique using a radiotracer called Sentimag-magtrace. The positive lymph node was located and removed to perform histologic analysis. In our study, we evaluate 100 patients who underwent breast cancer surgery. (3) Results: We calculated the identification rates of the different methods of sentinel lymph node detection and found that it was 88.9% using radioactive tracers vs. 89.5% using the magnetic tracer technology (Sentimag). (4) Conclusions: Thus, this technique avoids radiation exposure for both patients and health care providers, and can reduce costs and time.

An adapted protocol for magnetic localisation of nonpalpable breast cancer lesions and sentinel lymph nodes using a magnetic seed and superparamagnetic iron oxide tracer

BACKGROUND

Localisation techniques for nonpalpable breast cancer lesions and sentinel lymph node biopsy (SLNB) are associated with several drawbacks. A complete magnetic technique using magnetic seeds and superparamagnetic iron oxide tracer could be an interesting alternative. This study describes a clear protocol and the results of a combined magnetic approach.

METHODS

From August 2021 to February 2022 40 patients undergoing breast conserving surgery with SLNB were eligible for inclusion. Localisation was performed under ultrasound or stereotactic guidance, 1 week before surgery. Subsequently, 1 ml of tracer was injected at least 4 cm away from the tumour. Technetium-99m (^99m Tc) was injected 1 day before surgery as control procedure. Outcomes were SLNB time, a number of nodes detected with magnetic tracer including comparison with ^99m Tc, a success rate of malignant lesion detection and pathological margin assessment.

RESULTS

In total, 40 procedures were performed on 39 patients. A median of one node was retrieved. Sentinel nodes were retrieved using MagTrace® with a 92.5% detection rate compared to ^99m Tc. Wide local excision under magnetic guidance was successful in 35 cases.

CONCLUSIONS

This paper describes a combined magnetic approach for breast-conserving surgery and SLNB. An adapted protocol is described and could be used for implementation.

Combined use of magnetic seed and tracer in breast conserving surgery with sentinel lymph node biopsy for non-palpable breast lesions: A pilot study describing pitfalls and solutions

BACKGROUNDS

Traditionally, breast conserving surgery for non-palpable breast cancer is guided by wire or radioactive seed and radioactive tracer for sentinel lymph node biopsy (SLNB). Alternatively, a stain-less magnetic seed and superparamagnetic iron oxide tracer (SPIO) can be combined as a radioactive-free technique. The aim of this study was to define the pitfalls we encountered during implementation of this combined technique and provide solutions resulting in an instruction manual for a radio-active free procedure.

METHODS

Between January and March 2021, seventeen consecutive patients with cN0 non-palpable breast cancer were included. The magnetic seed was placed to localize the lesion and SPIO was used to identify the sentinel lymph node (SLN). A lymphoscintigraphy with Technetium-99m nano colloid was performed concomitantly in all patients as a control procedure for SPIO. Surgical outcomes are reported, including problems with placing and retrieval of the seed and SPIO and corresponding solutions.

RESULTS

Surgical excision was successful with invasive tumor-free margins in all patients. SLN detection was successful in 82% patients when compared to Technetium-99m. The most challenging issue was an overlapping magnetic signal of the seed and SPIO. Solutions are provided in detail.

CONCLUSIONS

Combined use of magnetic seed and SPIO for wide local excision and SLNB patients with non-palpable breast lesions appeared challenging due to overlapping magnetic signals. After multiple adaptations, the protocol proved to be feasible with an added advantage of eliminating the use of radioisotopes. We described the pitfalls and solutions resulting in an instruction manual for a totally radioactive-free procedure.

Evolution and refinement of magnetically guided sentinel lymph node detection in breast cancer: meta-analysis

BACKGROUND

Superparamagnetic iron oxide nanoparticles (SPIO) have been used as a tracer for sentinel lymph node (SLN) localization in breast cancer, demonstrating comparable performance to the combination of radioisotope (RI) and blue dye (BD).

METHODS

A systematic literature search and meta-analysis with subgroup and meta-regression analysis were undertaken to update the available evidence, assess technique evolution, and define knowledge gaps. Recommendations were made using the GRADE approach.

RESULTS

In 20 comparative studies, the detection rate was 97.5 per cent for SPIO and 96.5 per cent for RI ± BD (risk ratio 1.006, 95 per cent c.i. 0.992 to 1.019; P = 0.376, high-certainty evidence). Neoadjuvant therapy, injection site, injection volume or nodal metastasis burden did not affect the detection rate, but injection over 24 h before surgery increased the detection rate on meta-regression. Concordance was 99.0 per cent and reverse concordance 97.1 per cent (rate difference 0.003, 95 per cent c.i. -0.009 to 0.015; P = 0.656, high-certainty evidence). Use of SPIO led to retrieval of slightly more SLNs (pooled mean 1.96 versus 1.89) with a higher nodal detection rate (94.1 versus 83.5 per cent; RR 1.098, 1.058 to 1.140; P < 0.001; low-certainty evidence). In meta-regression, injection over 24 h before surgery increased the SPIO nodal yield over that of RI ± BD. The skin-staining rate was 30.8 per cent (very low-certainty evidence), and possibly prevented with use of smaller doses and peritumoral injection.

CONCLUSION

The performance of SPIO is comparable to that of RI ± BD. Preoperative injection increases the detection rate and nodal yield, without affecting concordance. Whether skin staining and MRI artefacts are reduced by lower dose and peritumoral injection needs to be investigated.