Superparamagnetic tracer and paramagnetic seed for marking of sentinel lymph nodes and index metastatic nodes before neoadjuvant chemotherapy to facilitate subsequent sentinel lymph node biopsy and targeted axillary dissection in breast cancer patients: A feasibility study

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Background/objective Axillary staging after neoadjuvant chemotherapy (NACT) is associated with low detection and high false negative rates for sentinel lymph node biopsies (SLNB). The optimal method for lymphatic mapping is not determined. The aim was to study the feasibility of pre-marking axillary lymph nodes before NACT with a paramagnetic approach, utilizing superparamagnetic iron oxide nanoparticles (SPIO) and paramagnetic seeds (Magseed®). Methods Eighty patients with clinically node negative (cN0) and node positive (cN+) breast cancers were included. All had SPIO injected before and technetium-99m (Tc 99 m ) after NACT. The index metastatic nodes (Index-met) were pre-marked with Magseed® ) . Primary endpoint was SLN and Index-met detection per patient. Secondary endpoints were concordance and reversed concordance of tracers. Results Thirty-nine cN0 and 37 cN+ patients who underwent SLNB and targeted axillary dissections (TAD) were eligible for analyses. The overall SLN detection with SPIO and Tc 99 m were: 65/76 (86 %) vs. 60/76 (79 %), (95 % CI for difference between tracers 1 %-12 %, p = 0.01) respectively. The overall concordance and reversed concordance were 84/106 (79 %) vs. 84/193 (49 %), (95 % CI 21 %-39 %, p < 0.001) respectively. Detection of Index-met with Magseed® and Tc 99 m were 36/37 (97 %) vs. 20/36 (56 %), (95 % CI 27 %-59 %, p < 0.001) respectively. The median number of nodes retrieved with SPIO and Tc 99 m were 2 (IQR 1–3) and 1 (IQR 1–2) (p < 0.001), respectively. Conclusions It was feasible to perform axillary staging by pre-marking the relevant lymph nodes using a paramagnetic approach before NACT. Notably, a large proportion of SPIO marked lymph nodes were different from those marked by Tc 99 m . Synopsis This study investigated using a paramagnetic approach for axillary nodal mapping before neoadjuvant chemotherapy comparing to a conventional mapping performed after chemotherapy. The results indicated feasibility of the paramagnetic method which also identified a different group of lymph nodes. However, these results require a further validation with a larger study.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.