Abstract: Objective To determine whether the complete clinical response(cCR) of  primary tumor evaluated by Magnetic resonance imaging(MRI)can predict a pathological complete response(pCR)results of axillary lymph nodes in biopsy-proven node-positive breast cancer following neoadjuvant chemotherapy(NAC).
Methods Patients with pathologically confirmed T1-3,N1-2 breast cancer underwent axillary lymph node dissection(ALND) after NAC were collected between October 2016 and October 2019.The response of NAC assessed by MRI of breast primary tumor in predicting axillary lymph node status was analyzed.
Results 95 consecutive node-positive breast cancer patients were collected.After NAC,the cCR rate of primary tumor was 41.1%(39/95) and the pCR rate of axillary lymph nodes was 47.4%(45/95).The sensitivity,specificity,negative predictive value and false negative rate of MRI were 82.0%(95%CI:68.1%-91.0%),66.7%(95%CI:50.9%-79.6%),76.9%(95%CI:60.3%-88.3%) and 18.0%(95%CI:9.0%-31.9%),respectively.However,the stratified analysis showed that the negative predictive value of the primary tumor MRI were 95.8%(95%CI:76.9%-99.8%) in Her-2 overexpression and triple negative patients,What's more,the false negative rate was 7.1%(95%CI:0-14.9%).
Conclusion The complete clinical response of breast primary tumor evaluated by MRI after NAC for node-positive breast cancer can not accurately predict a Negative pathological status of ALN.However,the stratified analysis shows that Her-2 overexpression and triple negative patients who achieve cCR can obtain a high negative predictive value and a low false negative rate.

Key words: breast cancer, lymph nodes metastasis, neoadjuvant chemotherapy, magnetic resonance imaging