Abstract
Simple SummaryIn 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.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.
Highlights
Sentinel lymph node dissection (SLND), referred to as sentinel lymph node biopsy, is the standard of care for clinically and radiologically node-negative breast cancer patients to stage the axilla and determine if cancer has spread to regional lymph nodes [1,2]
SLND was performed in 202 procedures (101 rats) except for two control animals in MRI experiments, and at least one popliteal lymph node was obtained with each procedure (Figure 1a)
This study looked at the timing of the injection and found that SPIO injections performed at a median of 16 days prior to SLND obtained a better identification rate (p = 0.031) and higher lymph node retrieval rate (p < 0.001) compared to injections on the morning of surgery
Summary
Sentinel lymph node dissection (SLND), referred to as sentinel lymph node biopsy, is the standard of care for clinically and radiologically node-negative breast cancer patients to stage the axilla and determine if cancer has spread to regional lymph nodes [1,2]. The current standard technique consists of a radioisotope and blue dye which are injected subcutaneously in the breast on the day of surgery [3]. This technique has some drawbacks including strict regulations regarding the use of radioisotopes and complications related to the use of blue dye [4]. This magnetic technique was shown to be non-inferior to the standard technique in several trials and meta-analyses [4,5,6,7,8,9,10,11,12,13,14,15,16,17]. There are different magnetic nanoparticles on the market but the most commonly used are Sienna+ (Endomag Ltd., Cambridge, UK), Magtrace (former SiennaXP, Endomag Ltd., Cambridge, UK) and Resovist (Schering AG, Berlin, Germany) with iron concentrations of 28.0, 28.0 and 27.9 mg/mL, respectively [18,19]
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