Improvement in breast magnetic resonance imaging after a sentinel procedure for breast cancer with superparamagnetic tracers

Does the presence of Magtrace preclude adaptive breast radiotherapy on an MR-Linac?

INTRODUCTION

This work reports on an unusual finding observed during image quality assessment in the preparation for the clinical implementation of breast magnetic resonance image-guided radiotherapy (MRIgRT) on a 1.5 Tesla (T) magnetic resonance linear accelerator (MR-Linac) (Elekta AB, Stockholm, Sweden).

CASE AND OUTCOMES

A patient with T2 N0 M0 right breast invasive ductal carcinoma, receiving adjuvant radiotherapy, underwent two imaging sessions on the MR-Linac. The imaging protocol included T1- and T2-weighted (W) turbo spin echo (TSE) sequences, a T1W mDixon, and a T2W TSE navigated sequence acquired on end-expiration. All images were reconstructed in the axial plane. Images were assessed for image quality and appropriateness for use within the treatment pathway using visual grading analysis (VGA). An artefact in the right breast was noted independently by all observers. The patient's skin and medical notes were reviewed for possible explanation. The findings were discussed with the patient's responsible clinician, and subsequent referral to the local multi-disciplinary team (MDT) for radiologist review was made. On further investigation, the patient's images demonstrated a signal void in the subareolar region of the right breast coinciding with the surgical site. This was distal from the tumour bed and deemed unlikely to be related to a Magseed marker or intraoperative clips. The patient reported no history of nipple tattoo or piercing. There was nothing on clothing that this could be attributed to.

DISCUSSION

Following MDT review, where all potential sources of signal void were considered, it was concluded that the cause was Magtrace, a superparamagnetic iron oxide tracer, recommended for sentinel lymph node localisation in patients with breast cancer in the United Kingdom. The artefact was characteristic of a magnetic susceptibility artefact. These can arise from local magnetic field inhomogeneities caused by the presence of the metal compounds in MagTrace. For breast MRIgRT on the MR-Linac, treatment verification and the possibility of real-time replanning is a critical aspect. The magnetic susceptibility artefact significantly inhibited plan adaption and confidence in the online image registration process making the patient ineligible for treatment on the MR-Linac.

CONCLUSION

As part of ongoing work-up for breast MRIgRT, the screening of patients for Magtrace is now included. Optimisation of MR imaging sequences for radiotherapy planning and image review to minimise distortion are being developed.

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.

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.

The Application of Magnetic Nanoparticles for Sentinel Lymph Node Detection in Clinically Node-Negative Breast Cancer Patients: A Systemic Review and Meta-Analysis

Superparamagnetic iron oxide (SPIO), an alternative mapping agent, can be used to identify sentinel lymph nodes in patients with clinically node-negative breast cancer. However, its performance in comparison with the standard method, using a radioisotope (technetium-99 m, Tc) alone or in combination with blue dye, remains controversial. Hence, a systematic review and meta-analysis were conducted to evaluate the diagnostic accuracy of SPIO and its clinical impact in the management of breast cancer. The PubMed, Embase, and Cochrane databases were comprehensively searched from inception to 1 May 2022. Cohort studies regarding the comparison of SPIO with standard methods for sentinel lymph node identification were included. A total of 19 prospective cohort studies, which collectively included 2298 clinically node-negative breast cancer patients undergoing sentinel lymph node identification through both the standard method and SPIO, were identified. The detection rate for sentinel lymph nodes (RR, 1.06; 95% CI, 1.05−1.08; p < 0.001) was considerably higher in the SPIO cohorts than in the standard method cohorts, although this difference was not significant in detected patients, patients with positive sentinel lymph nodes, or positive sentinel lymph nodes. Compared with the standard method, the SPIO method could be considered as an alternative standard of care for sentinel lymph node detection in patients with clinically node-negative breast cancer.

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

BACKGROUND

A procedure for sentinel lymph node biopsy (SLNB) using superparamagnetic iron-oxide (SPIO) nanoparticles and intraoperative sentinel lymph node (SLN) detection was developed to overcome drawbacks associated with the current standard-of-care SLNB. However, residual SPIO nanoparticles can result in void artefacts at follow-up magnetic resonance imaging (MRI) scans. We present a grading protocol to quantitatively assess the severity of these artefacts and offer an option to minimise the impact of SPIO nanoparticles on diagnostic imaging.

METHODS

Follow-up mammography and MRI of two patient groups after a magnetic SLNB were included in the study. They received a 2-mL subareolar dose of SPIO (high-dose, HD) or a 0.1-mL intratumoural dose of SPIO (low-dose, LD). Follow-up mammography and MRI after magnetic SLNB were acquired within 4 years after breast conserving surgery (BCS). Two radiologists with over 10-year experience in breast imaging assessed the images and analysed the void artefacts and their impact on diagnostic follow-up.

RESULTS

A total of 19 patients were included (HD, n = 13; LD, n = 6). In the HD group, 9/13 patients displayed an artefact on T1-weighted images up to 3.6 years after the procedure, while no impact of the SPIO remnants was observed in the LD group.

CONCLUSIONS

SLNB using a 2-mL subareolar dose of magnetic tracer in patients undergoing BCS resulted in residual artefacts in the breast in the majority of patients, which may hamper follow-up MRI. This can be avoided by using a 0.1-mL intratumoural dose.

How molecular imaging will enable robotic precision surgery : The role of artificial intelligence, augmented reality, and navigation

Molecular imaging is one of the pillars of precision surgery. Its applications range from early diagnostics to therapy planning, execution, and the accurate assessment of outcomes. In particular, molecular imaging solutions are in high demand in minimally invasive surgical strategies, such as the substantially increasing field of robotic surgery. This review aims at connecting the molecular imaging and nuclear medicine community to the rapidly expanding armory of surgical medical devices. Such devices entail technologies ranging from artificial intelligence and computer-aided visualization technologies (software) to innovative molecular imaging modalities and surgical navigation (hardware). We discuss technologies based on their role at different steps of the surgical workflow, i.e., from surgical decision and planning, over to target localization and excision guidance, all the way to (back table) surgical verification. This provides a glimpse of how innovations from the technology fields can realize an exciting future for the molecular imaging and surgery communities.

Introducing SentiMag in a rural setting: A 5-year experience

BACKGROUND

The Sentimag device is a probe that contains a sensitive magnetometer which detects either an implantable magnetic marker (MagSeed) or an infectable superparamagnetic ironoxide nanoparticle tracer (MagTrace). MagSeed is used to localise impalpable breast lesions; MagTrace is used to identify sentinel lymph nodes. In Australasia, Sentinel lymph node (SLN) biopsy, using radioactive colloid injection, is a mainstay of prognostication in breast surgery in patients with a clinically negative axilla. In addition, radioactive seeds or hookwires have been used to detect impalpable breast lesions. Gisborne Hospital has been using the SentiMag device since June 2016 to both identify sentinel lymph nodes (Magtrace) and impalpable tumours (Magseed). This study gives perspective over more than 5 years on how this new technology can benefit patients and clinicians in the rural setting.

METHODS

Patient data had been collected by the operative surgeon prospectively and corroborated with the coding department. Consecutive cases performed by a single surgeon were included in this study. Inclusion criteria were: (1) any patient who needed localisation of an impalpable breast lesion; (2) any patient who needed a sentinel lymph node biopsy; (3) cases were collected from January 2013 with the large majority of cases were collected between January 2015 and Jan 2020. Comparisons were made between patients with different localisation methods. Basic demographics were collected at the time of the surgery and outcomes then recorded. Staging, lymph node status, lymph node detection rates and complications were collected. Mode of tumour and sentinel node location was recorded. Financial data was collected from administrative staff via receipts and invoices of purchases to the hospital.

RESULTS

Of the 125 patients included in this study: 23 underwent magnetic seed insertion; 15 underwent a hookwire insertion; 45 cases used MagTrace injection; 71 cases used radioactive colloid injection. There was a significantly higher detection rate of two or more sentinel nodes in the SentiMag group. (91% vs. 71.8%, p = 0.01). Neither complication rates, nor cancer detection rates were significantly different. Eighty-four (67.2%) cases did not require tumour location.

CONCLUSION

SentiMag is safe to use in a rural setting. Using the SentiMag system can simplify care for patients and surgeons and was shown to be cost effective in our hospital.

Laparoscopic Probe for Sentinel Lymph Node Harvesting using Magnetic Nanoparticles

OBJECTIVE

Sentinel lymph node harvesting is an essential step in the surgical treatment of a growing number of malignancies. Various techniques are available to facilitate this purpose. The present study reports a new laparoscopic technique for lymph node harvesting using magnetic nanoparticles containing a superparamagnetic iron-oxide core and dextran coating. This study assesses the clinical relevance of the prototype and provides input for further technological development on the way to clinical implementation.

METHODS

A laparoscopic differential magnetometer prototype was built, utilizing a nonlinear detection principle (differential magnetometry) for magnetic identification of lymph nodes. The iron content sensitivity, depth & spatial sensitivity, and angular sensitivity were analyzed to investigate clinical options.

RESULTS

The minimum detectable amount of iron was 9.8 g at a distance of 1 mm. The detection depth was 5, 8, and 10 mm for samples containing 126, 252, and 504 g iron, respectively. The maximum lateral detection distance was 5, 7, and 8 mm for samples containing 126, 252, and 504 g iron, respectively. A sample containing 504 g iron was detectable at all angulations assessed (0, 30, 60 and 90).

CONCLUSION

The laparoscopic differential magnetometer demonstrates promising results for further investigation and development towards laparoscopic lymph node harvesting using magnetic nanoparticles.

SIGNIFICANCE

The laparoscopic differential magnetometer facilitates a novel method for sentinel lymph node harvesting, which helps to determine prognosis and treatment of cancer patients.

Re-evaluation of Sentinel Lymph Node Biopsy for Melanoma

OPINION STATEMENT

The vast majority of patients newly diagnosed with melanoma present with clinically localized disease, and sentinel lymph node biopsy (SLNB) is a standard of care in the management of these patients, particularly in intermediate thickness cases, in order to provide important prognostic data. However, SLNB also has an important role in the management of patients with other subtypes of melanoma such as thick melanomas, certain thin melanomas, and specific histologic variants of melanoma such as desmoplastic melanoma. Furthermore, there have been technical advances in the SLNB technique, such as the development of newer radiotracers and use of SPECT/CT, and there is some data to suggest performing a SLNB may be therapeutic. Finally, the management of patients with a positive sentinel lymph node (SLN) has undergone dramatic changes over the past several years based on the results of recent important clinical trials. Treatment options for patients with SLN metastases now include surveillance, completion lymph node dissection, and adjuvant therapy with checkpoint inhibitors and targeted therapy. SLNB continues to play a crucial role in the management of patients with melanoma, allowing for risk stratification, potential regional disease control, and further treatment options for patients with a positive SLN.

Effects of iron oxide particles on MRI and mammography in breast cancer patients after a sentinel lymph node biopsy with paramagnetic tracers

OBJECTIVE

The aim of this study is to evaluate the effect of iron oxide particle deposition on follow-up mammograms and MRI examinations of patients who underwent sentinel lymph node detection with iron oxide particles.

MATERIALS AND METHODS

Two hundred and eighteen patients who had sentinel lymph node biopsy (SLNB) with iron oxide particles were evaluated. Follow-up MRI and mammography were available in 36 and 69 cases respectively. MRI examinations were evaluated for ferromagnetic artifacts that were graded as follows: 0 = No artifact, 1 = Focal area, 2 = Segmental and 3 = Regional signal void artifact. Mammography artifacts were evaluated for the presence of dense particles. Pearson's chi-square test was used for statistical analyses and P < 0.05 was accepted as significant.

RESULTS

MRI artifact grading was as follows: Grade 0: 11 (30.6%), Grade 1: 14 (38.9%), Grade 2: 3 (8.3%), and Grade 3: 8 (22.2%). The grade of artifacts differed across surgery types (P = 0.019). Grade 3 artifacts were higher in breast conserving cases whereas Grade 0 was more frequent in subcutaneous mastectomy cases. Three out of 69 (4.4%) cases who had follow-up mammography had artifacts due to iron oxide particle accumulation which presented as Grade 3 MRI artifact in all.

CONCLUSION

Accumulation of iron oxide particles after SLNB with paramagnetic tracers causes artifacts on follow-up MRI examinations in half of the cases but it is significantly low in mammograms. These artifacts may be confusing in the evaluation of the images. Radiologists must be aware of these tracers and their artifacts whereas patients should be questioned for the type of SLNB before a follow-up examination.

Superparamagnetic Iron Oxide Sentinel Node Tracer Injection: Effects on Breast MRI Quality

OBJECTIVE

To evaluate the MRI artifact rendered by the typical injection of a ferromagnetic tracer now being intermittently used for intraoperative sentinel node (SN) identification at our institution, and to explore its impact on postoperative imaging and management.

METHODS

This study was Institutional Review Board-approved and granted a waiver of consent. A database search tool was used to identify MRI exams performed on patients who had previously undergone breast-conserving surgery with use of a superparamagnetic iron oxide (SPIO) SN tracer between January 1, 2015, and May 1, 2020. MRI reports, images, and relevant demographic, oncologic, and surgical history were collected. The presence or absence of SPIO residue on breast MRI, as well as its impact on image quality, were extracted from the prospective reports.

RESULTS

A total of 21 MRI exams were identified in 16 patients who had undergone breast-conservation therapy for cancer with use of SPIO SN tracer. Mean time from particle injection to baseline postoperative MRI exam was 10.8 months. All reports (21/21) noted evidence of SPIO residue. Of these, 5/21 were assessed as non-diagnostic; the remainder were assessed as limited.

CONCLUSION

Radiologists should be aware of the use of superparamagnetic tracers for SN identification and the impact on the quality of future MRI examinations. Alternative injection approaches are being developed and sequence parameters adjusted to minimize artifact.

A randomized study comparing different doses of superparamagnetic iron oxide tracer for sentinel lymph node biopsy in breast cancer: The SUNRISE study

INTRODUCTION

The non-radioactive method that uses the magnetic tracer (SPIO/Sienna) has shown to be a feasible technique for the SLN detection in breast cancer patients. The aim of this study is to assess the efficacy of different doses of a new magnetic tracer Sienna XP (Magtrace) compared to Tc-99 m and to evaluate its non-inferiority.

METHODS

Patients diagnosed with early-stage breast cancer cT1-3 N0, from October 2016 to August 2018 were eligible and consecutively randomized to three different doses of new SPIO used: group 1 (1 mL), group 2 (1.5 mL) and group 3 (2 mL).

RESULTS

A total of 135 patients were included in the study, 45 in each group. Detection of SLNs with the three doses of Sienna XP (1 mL, 1.5 mL and 2 mL) showed non-inferior rates compared to the conventional technique with radiotracer (p = 0.654). Concordance by patients with SLN positive was 100% for all groups. 83 (70.3%) patients reported skin staining at one month postoperatively, significantly lower in group 1 (p = 0.042). At 6 months follow up, group 1 remains with significantly lower skin discoloration (p = 0,01). In multivariate analysis, dose of 2 mL showed statistically significant for the skin staining. The majority of patients (70%) felt that skin discoloration does not represent a problem.

CONCLUSION

The use of the Sienna XP magnetic tracer at 1 mL is not inferior to higher doses of magnetic tracer neither is inferior to radiotracer. 1 mL of magnetic tracer resulted in significantly less skin discoloration compared to higher doses.

Horizons of nanotechnology applications in female specific cancers

Female-specific cancers are the most common cancers in women worldwide. Early detection methods remain unavailable for most of these cancers, signifying that most of them are diagnosed at later stages. Furthermore, current treatment options for most female-specific cancers are surgery, radiation and chemotherapy. Although important milestones in molecularly targeted approaches have been achieved lately, current therapeutic strategies for female-specific cancers remain limited, ineffective and plagued by the emergence of chemoresistance, which aggravates prognosis. Recently, the application of nanotechnology to the medical field has allowed the development of novel nano-based approaches for the management and treatment of cancers, including female-specific cancers. These approaches promise to improve patient survival rates by reducing side effects, enabling selective delivery of drugs to tumor tissues and enhancing the uptake of therapeutic compounds, thus increasing anti-tumor activity. In this review, we focus on the application of nano-based technologies to the design of novel and innovative diagnostic and therapeutic strategies in the context of female-specific cancers, highlighting their potential uses and limitations.