4. Analysis of void artefacts in post-operative breast MRI due to residual SPIO after magnetic SLNB in SentiMAG Trial participants

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.

Feasibility of Magnetic Technique for Axillary Staging after Neoadjuvant Therapy in Breast Cancer Patients

PURPOSE

Optimal axillary staging after neoadjuvant chemotherapy (NAC) in node-negative breast cancer is an area of controversy. Sentinel node biopsy with Technetium-sulphur colloid (99m Tc) alone or with blue dye is the recommended technique for evaluating axilla in these patients. However, this technique has drawbacks such as limited access to nuclear departments and timing limitations related to Tc injection exposing patients to unnecessary radiation. Superparamagnetic iron oxide nanoparticles (SPIO) may represent a valid option for SLN biopsy. In this study, we assessed the feasibility of the magnetic technique (Sentimag) with combination of isosulfan blue dye in breast cancer patients who received NAC.

METHODS

The study sample consisted of 54 female breast cancer patients who received NAC. Sentinel node localization was performed using magnetic technique and blue dye. Sentinel node identification rate (IFR) of magnetic technique was calculated and postoperative complications were assessed.

RESULTS

Sentinel lymph node was detected in 52 patients with Sentimag method (identification rate = 96.3%, 95% CI: 87.4-98.9%). Blue dye was successful to find SLN in 38 patients (identification rate = 70%). The most common histologic type was invasive ductal (n = 51; 94.4%). Mean tumor size was 2.1 cm after NAC. Most of patients had T2 (n = 30; 55.5%) and HER2 + positive (n = 49; 90.7%) cancer.

CONCLUSION

Sentimag which is a magnetic technique appears to be safe, easy to perform with minimal adverse effects, may be an alternative and accurate technique in patients with NAC, especially in breast units where nuclear medicine unit is not available.

Supplemental data for this article is available online at https://doi.org/10.1080/08941939.2022.2038737 .

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.

Optimization of SPIO Injection for Sentinel Lymph Node Dissection in a Rat Model

The magnetic technique, consisting of a magnetic tracer and a handheld magnetometer, is a promising alternative technique for sentinel lymph node dissection (SLND) and was shown to be non-inferior to the standard technique in terms of identification rates. In this study, injection characteristics (iron dose, dilution, time course and massaging) were evaluated to optimize magnetic tracer uptake in the sentinel lymph nodes (SLN) in a rat hindleg model. 202 successful SLNDs were performed. Iron uptake in the SLN is proportional (10% utilization rate) to the injection dose between 20 and 200 μg, showing a plateau uptake of 80 μg in the SLN around 1000 μg injection. Linear regression showed that time had a higher impact than dilution, on the SLN iron uptake. Massaging showed no significant change in iron uptake. The amount of residual iron at the injection site was also proportional to the injection dose without any plateau. Time was a significant factor for wash-out of residual iron. From these results, preoperative injection may be advantageous for SLN detection as well as reduction in residual iron at the injection site by potential decrease in required injection dose.

Optimization of SPIO Injection for Sentinel Lymph Node Dissection in a Rat Model

Simple Summary

In this study, the following injection characteristics were evaluated to optimize magnetic tracer uptake in the sentinel lymph nodes (SLN) in a rat hindleg model: (a) iron dose, (b) effect of dilution, (c) effect of injecting at different time courses and (d) effect of massaging the injection site. In conclusion, injection dose and time were primary factors for the SLN iron uptake. The result from this study will provide a background for magnetic procedures.

Abstract

The magnetic technique, consisting of a magnetic tracer and a handheld magnetometer, is a promising alternative technique for sentinel lymph node dissection (SLND) and was shown to be non-inferior to the standard technique in terms of identification rates. In this study, injection characteristics (iron dose, dilution, time course and massaging) were evaluated to optimize magnetic tracer uptake in the sentinel lymph nodes (SLN) in a rat hindleg model. 202 successful SLNDs were performed. Iron uptake in the SLN is proportional (10% utilization rate) to the injection dose between 20 and 200 μg, showing a plateau uptake of 80 μg in the SLN around 1000 μg injection. Linear regression showed that time had a higher impact than dilution, on the SLN iron uptake. Massaging showed no significant change in iron uptake. The amount of residual iron at the injection site was also proportional to the injection dose without any plateau. Time was a significant factor for wash-out of residual iron. From these results, preoperative injection may be advantageous for SLN detection as well as reduction in residual iron at the injection site by potential decrease in required injection dose.

The Turkish SentiMAG feasibility trial: preliminary results

BACKGROUND

Sentinel node biopsy (SNB) is the standard of care for staging of the clinically and radiologically negative axillary lymph nodes in breast cancer patients. Sentinel node biopsy, with using Technetium-sulphur colloid (99 m Tc) alone or with blue dye is standard technique for evaluating axillary lymph nodes. This technique has drawbacks such as radiation exposure. Superparamagnetic iron oxide nanoparticles (SPIO) can represent a valid option for SNB. In this study; we tried to evaluate feasibility of new magnetic technique in Turkish early breast cancer patients.

MATERIAL AND METHODS

The study sample consists of 143 women affected by early breast carcinoma with clinically negative axillary lymph nodes. Sentinel node localization was performed using magnetic technique. Detection rate of magnetic technique was calculated and postoperative complications were assessed.

RESULTS

Results are based on 104 patients. Sentinel node identification rate was 99% (103/104, 95% CI 0.97-1.01) for magnetic technique. A median of two SNs per patient was removed. Major adverse reaction was the permanent skin coloration (7.1%).

CONCLUSIONS

The magnetic technique is a feasible method for detecting SN in breast cancer patients with minimal adverse effects. Magnetic technique may be alternative to standard technique especially in breast units, where nuclear medicine unit is not available.

Handheld magnetic probe with permanent magnet and Hall sensor for identifying sentinel lymph nodes in breast cancer patients

The newly developed radioisotope-free technique based on magnetic nanoparticle detection using a magnetic probe is a promising method for sentinel lymph node biopsy. In this study, a novel handheld magnetic probe with a permanent magnet and magnetic sensor is developed to detect the sentinel lymph nodes in breast cancer patients. An outstanding feature of the probe is the precise positioning of the sensor at the magnetic null point of the magnet, leading to highly sensitive measurements unaffected by the strong ambient magnetic fields of the magnet. Numerical and experimental results show that the longitudinal detection length is approximately 10 mm, for 140 μg of iron. Clinical tests were performed, for the first time, using magnetic and blue dye tracers—without radioisotopes—in breast cancer patients to demonstrate the performance of the probe. The nodes were identified through transcutaneous and ex-vivo measurements, and the iron accumulation in the nodes was quantitatively revealed. These results show that the handheld magnetic probe is useful in sentinel lymph node biopsy and that magnetic techniques are widely being accepted as future standard methods in medical institutions lacking nuclear medicine facilities.

Meta-analysis of sentinel lymph node biopsy in breast cancer using the magnetic technique

BACKGROUND

The standard for sentinel lymph node biopsy (SLNB), the dual technique (radiolabelled tracer and blue dye), has several drawbacks. A novel magnetic technique without these drawbacks has been evaluated in a number of clinical trials. It uses a magnetic tracer and a handheld magnetometer to identify and excise sentinel lymph nodes. A systematic review and meta-analysis was performed to assess the performance and utility of the magnetic in comparison to the standard technique.

METHODS

MEDLINE, PubMed, Embase and the Cochrane online literature databases were used to identify all original articles evaluating the magnetic technique for SLNB published up to April 2016. Studies were included if they were prospectively conducted clinical trials comparing the magnetic with the standard technique for SLNB in patients with breast cancer.

RESULTS

Seven studies were included. The magnetic technique was non-inferior to the standard technique (z = 3·87, P < 0·001), at a 2 per cent non-inferiority margin. The mean identification rates for the standard and magnetic techniques were 96·8 (range 94·2-99·0) and 97·1 (94·4-98·0) per cent respectively (risk difference (RD) 0·00, 95 per cent c.i. -0·01 to 0·01; P = 0·690). The total lymph node retrieval was significantly higher with the magnetic compared with the standard technique: 2113 (1·9 per patient) versus 2000 (1·8 per patient) (RD 0·05, 0·03 to 0·06; P = 0·003). False-negative rates were 10·9 (range 6-22) per cent for the standard technique and 8·4 (2-22) per cent for the magnetic technique (RD 0·03, 0·00 to 0·06; P = 0·551). The mean discordance rate was 3·9 (range 1·7-6·9) per cent.

CONCLUSION

The magnetic technique for SLNB is non-inferior to the standard technique, with a high identification rate but with a significantly higher lymph node retrieval rate.

Sentinel lymph node identification using superparamagnetic iron oxide particles versus radioisotope: The French Sentimag feasibility trial

BACKGROUND AND OBJECTIVES

The French Sentimag feasibility trial evaluated a new method for the localization of breast cancer sentinel lymph node (SLN) using Sienna+®, superparamagnetic iron oxide particles, and Sentimag® detection in comparison to the standard technique (isotopes ± blue dye).

METHODS

We conducted a prospective multicentric paired comparison trial on 115 patients. SLN localization was performed using both the magnetic technique and the standard method. Detection rate and concordance between magnetic and standard tracers were calculated. Post-operative complications were assessed after 30 days.

RESULTS

Results are based on 108 patients. SLN identification rate was 98.1% [93.5-99.8] for both methods, 97.2% [92.1-99.4] for Sienna+® and 95.4% [89.5-98.5] for standard technique. A mean of 2.1 SLNs per patient was removed. The concordance rate was 99.0% [94.7-100.0%] per patient and 97.4% [94.1-99.2] per node. Forty-six patients (43.4%) had nodal involvement. Among involved SLNs, concordance rate was 97.7% [88.0-99.9] per patient and 98.1% [90.1-100.0] per node.

CONCLUSIONS

This new magnetic tracer is a feasible method and a promising alternative to the isotope. It could offer benefits for ambulatory surgery or sites without nuclear medicine departments. J. Surg. Oncol. 2016;113:501-507. © 2016 Wiley Periodicals, Inc.

Magnetic sentinel lymph node biopsy in a murine tumour model

The magnetic technique for sentinel node biopsy provides a radioisotope-free alternative for staging breast cancer. It requires refinement to reduce "residual iron content" at injection sites by maximising lymphatic uptake to prevent "void artefacts" on magnetic resonance imaging (MRI), which could adversely affect clinical use. The site and timing of injection of magnetic tracer was evaluated in a murine tumour model (right hind limb) in 24 wild type mice. Right-sided intratumoural and left sided subcutaneous injection of magnetic tracer and assessment of nodal iron uptake on MRI, surgical excision and histopathological grading at time frames up to 24 hours were performed. Rapid iron uptake on MRI, smaller "void artefacts"(P<0.001) and a significant increase in iron content with time were identified in the subcutaneous injection group (r=0.937; P<0.001).Subcutaneous injection and increasing delay between tracer injection and surgery is beneficial for lymphatic iron uptake.

FROM THE CLINICAL EDITOR

Sentinel lymph node biopsy (SLNB) has been the standard of care in breast cancer management for some time. Recent development has seen the introduction of magnetic tracer for SLNB. In this article, the authors investigated the refined use of magnetic tracer in determining the optimal timing of administration and the location of injection. The findings should provide more data on the future use of this new technique.