The magnetic technique is a feasible technique for SLNB, with an identification rate that is not inferior to the standard technique.

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.

Background: Non-palpable breast cancers require localization-guided surgery and axillary staging using sentinel lymph node biopsy (SLNB). This study investigated the novel technique of magnetic-guided lesion localization and concurrent SLNB, which avoids the need for wire-guided localization and radioisotopes.Methods: An ultrasound-guided intratumoral injection of magnetic tracer (0⋅5 ml) was performed in a protocol-driven predefined minimum of ten patients with palpable breast cancer to assess the ability of the magnetic tracer safely to localize the tumour at the site of injection and concurrently drain to the lymphatics. Once successful lesion localization had been confirmed (peak magnetometer count retained at the centre of the tumour), the technique was undertaken in a further 20 patients with non-palpable breast cancers awaiting wide local excision and SLNB. All patients underwent SLNB with both the magnetic and standard dual (radioisotope and Patent Blue V dye) techniques.Results: Thirty-two patients were recruited, of whom 12 (1 with bilateral disease) presented with palpable and 20 with non-palpable breast cancer. Peak magnetometer counts were retained at the tumour centre in all palpable (13) and non-palpable (20) breast cancers. Re-excisions for involved margins were necessary in two patients with non-palpable breast cancers. The sentinel lymph node identification rates were 28 of 33 procedures for the magnetic technique alone, 32 of 33 for the magnetic technique combined with blue dye, and 32 of 33 for the standard dual technique.Conclusion: Magnetic lesion localization is feasible, with intratumoral magnetic tracer injection combined with a periareolar injection of blue dye for subsequent SNLB. * Other members of the MagSNOLL Trialists Group are co-authors of this study and can be found under the heading Collaborators

Introduction Breast cancer staging with sentinel lymph node biopsy relies on the use of radioisotopes, which limits the availability of the procedure worldwide. The use of a magnetic nanoparticle tracer and a handheld magnetometer provides a radiation-free alternative, which was recently evaluated in two clinical trials. The hydrodynamic particle size of the used magnetic tracer differs substantially from the radioisotope tracer and could therefore benefit from optimization. The aim of this study was to assess the performance of three different-sized magnetic nanoparticle tracers for sentinel lymph node biopsy within an in vivo porcine model. Materials and methods Sentinel lymph node biopsy was performed within a validated porcine model using three magnetic nanoparticle tracers, approved for use in humans (ferumoxytol, with hydrodynamic diameter d H =32 nm; Sienna+ ® , d H =59 nm; and ferumoxide, d H =111 nm), and a handheld magnetometer. Magnetometer counts (transcutaneous and ex vivo), iron quantification (vibrating sample magnetometry), and histopathological assessments were performed on all ex vivo nodes. Results Transcutaneous “hotspots” were present in 12/12 cases within 30 minutes of injection for the 59 nm tracer, compared to 7/12 for the 32 nm tracer and 8/12 for the 111 nm tracer, at the same time point. Ex vivo magnetometer counts were significantly greater for the 59 nm tracer than for the other tracers. Significantly more nodes per basin were excised for the 32 nm tracer compared to other tracers, indicating poor retention of the 32 nm tracer. Using the 59 nm tracer resulted in a significantly higher iron accumulation compared to the 32 nm tracer. Conclusion The 59 nm tracer demonstrated rapid lymphatic uptake, retention in the first nodes reached, and accumulation in high concentration, making it the most suitable tracer for intraoperative sentinel lymph node localization.

The standard for the treatment of early non-palpable breast cancers is wide local excision directed by wire-guided localization and sentinel lymph node biopsy (SLNB). This has drawbacks technically and due to reliance upon radioisotopes. We evaluated the use of a magnetic tracer for its localization capabilities and concurrent performance of SLNB using a handheld magnetometer in a porcine model as a novel alternative to the current standard. Ethical approval by the IRCAD Ethics Review Board, Strasbourg (France) was received. A magnetic tracer was injected in varying volumes (0.1-5 mL) subcutaneously into the areolar of the left and right 3rd inguinal mammary glands in 16 mini-pigs. After 4 h magnetometer counts were taken at the injection sites and in the groins. The magnetometer was used to localize any in vivo signal from the draining inguinal lymph nodes. Magnetic SLNB followed by excision of the injection site was performed. The iron content of sentinel lymph nodes (SLNs) were graded and quantified. All excised specimens were weighed and volumes were calculated. Univariate analyses were performed to evaluate correlation. Magnetic SLNB was successful in all mini-pigs. There was a significant correlation (r = 0.86; p < 0.01) between magnetometer counts and iron content of SLNs. Grading of SLNs on both H&E and Perl's staining correlated significantly with the iron content (p = 0.001; p = 0.003) and magnetometer counts (p < 0.001; p = 0.004). The peak counts corresponded to the original magnetic tracer injection sites 4 h after injection in all cases. The mean volume and weight of excised injection site specimens was 2.9 cm(3) (SD 0.81) and 3.1 g (SD 0.85), respectively. Injection of ≥0.5 mL magnetic tracer was associated with significantly greater volume (p = 0.05) and weight of excision specimens (p = 0.01). SLNB and localization can be performed in vivo using a magnetic tracer. This could provide a viable alternative for lesion localization and concurrent SLNB in the treatment of non-palpable breast cancer.

Longer follow-up data from existing trials, optimization of patient criteria and cost-effectiveness analyses are needed. Based on the current evidence, IORT can be offered as an alternative to EBRT to selected patients within agreed protocols, and outcomes should be monitored within national registries.

The combined technique (radioisotope and blue dye) is the gold standard for sentinel lymph node biopsy (SLNB) and there is wide variation in techniques and blue dyes used. We performed a systematic review and meta-analysis to assess the need for radioisotope and the optimal blue dye for SLNB. A total of 21 studies were included. The SLNB identification rates are high with all the commonly used blue dyes. Furthermore, methylene blue is superior to iso-sulfan blue and Patent Blue V with respect to false-negative rates. The combined technique remains the most accurate and effective technique for SLNB. In order to standardize the SLNB technique, comparative trials to determine the most effective blue dye and national guidelines are required.

The magnetic technique is feasible for SLNB in melanoma with a high SLN identification rate, but is associated with skin staining. When compared with the standard dual technique, it did not reach our predefined non-inferiority margin.