Clinical study - Sein Néoadjuvant

Sentinel lymph node dissection (SLND) after NAC, aimed to reduce the rate of unnecessary axillary lymphadenectomy, is not a standard of care in case of patient with previously involved node before NAC because of a too high false negative rate (FNR).;Clinical consequences of FNR of SLND after NAC are currently unknown. Consequently, contrary to adjuvant setting, a risk of SLND false negative case after NAC is not acceptable.;GANEA3 aims to evaluate the results of an innovative multiparametric strategy combining (1) an identification before chemotherapy of a lymph node involvement using a metal clip and then its analysis after treatment, (2) the analysis of sentinel lymph node (SLN) after NAC, and (3) analysis of biological parameters of breast tumor before and after NAC, to predict axillary status after NAC. This will identify patients with initial lymph node involvement who could benefit from SLN after NAC without additional axillary dissection with a very low FNR (í_1%).;The most "pathological" metastatic lymph node will be identified with a metal clip under ultrasound. They will then receive a NAC before breast and axillary surgery. An assessment of the NAC response at the breast and axillary will be performed by imagery. Then, all patients undergo the resection of the tagged axillary node with the metal clip, SLN detection and biopsy and a complementary axillary lymphadenectomy.