Background: Axillary lymph node status provides important staging information. We sought to evaluate the predictive value of breast magnetic resonance imaging (MRI) in detecting axillary lymph node metastases prior to initiation of neoadjuvant chemotherapy (NAC) and in detecting residual lymph node metastases after NAC in women found to be node positive prior to NAC.
Methods: Women underwent breast MRI with axillary evaluation prior to initiation of NAC and again after completion of NAC. Pathologic confirmation of lymph node status was confirmed by sentinel lymph node biopsy (SLNB), image-guided axillary fine-needle aspiration (FNA)/core biopsy, or axillary lymph node dissection. We evaluated the sensitivity, specificity, and negative and positive predictive values of MRI in detecting axillary node involvement.
Results: Seventy-four women completed NAC and underwent surgery. Sensitivity of MRI in detecting axillary node involvement prior to NAC was 64.7% and specificity was 100%, with positive and negative predictive values of MRI of 100% and 77.8%, respectively. Sensitivity and specificity of MRI to identify residual pathologic axillary lymph node disease following NAC were 85.7% and 89%, respectively, while the positive and negative predictive values were 92% and 80.9%, respectively.
Conclusion: Breast MRI has moderate sensitivity and high specificity for predicting axillary lymph node status prior to NAC. In patients found to be node positive prior to NAC, MRI was able to predict with moderate sensitivity and specificity whether residual nodal disease was present. The accuracy of MRI is not adequate to obviate either the need for staging by sentinel node biopsy or the need for completion axillary dissection in women determined to be node positive prior to NAC.