[Sentinel node biopsy after neoadjuvant chemotherapy in breast cancer. Its relation with molecular subtypes]. / La biopsia del ganglio centinela después de quimioterapia neoadyuvante en el cáncer de mama. Relación con los subtipos moleculares.

ABSTRACT

OBJECTIVE: To evaluate the influence of the molecular subtype (MS) in the Sentinel Node Biopsy (SNB) technique after neoadjuvant chemotherapy (NAC) in women with locally advanced breast cancer (BC) and a complete axillary response (CR). MATERIAL AND METHODS: A prospective study involving 70 patients with BC treated with NAC was carried out. An axillary lymph node dissection was performed in the first 48 patients (validation group VG), and in case of micro- or macrometastases in the therapeutic application phase (therapy groupTG). Classified according to MS 14 luminal A; 16 luminal B HER2-, 13 luminal B HER2+, 10HER2+ non-luminal, 17 triple-negative. RESULTS: SNB was carried out in 98.6% of the cases, with only one false negative result in the VG (FN=2%). Molecular subtype did not affect SN detection. Despite the existence of axillary CR, statistically significant differences were found in the proportion of macrometastasis (16.7% vs. 35.7%, p=0.043) on comparing the pre-NAC cN0 and cN+. Breast tumor response to NAC varied among the different MS, this being lowest in luminal A (21.5%) and highest in non-luminal HER2+ group (80%). HER2+ and triple-negative were the groups with the best axillary histological response both when there was prior clinical involvement and when there was not. CONCLUSIONS: Molecular subtype is a predictive factor of the degree of tumor response to NAC in breast cancer. However, it does not affect SNB detection and efficiency. SNB can also be used safely in women with prior node involvement as long as a complete clinical and radiological assessment is made of the node response to NAC.