Axillary lymph node status is an important prognostic factor for breast cancer patients. This study aimed to assess the accuracy of MRI in assessing the axillary nodal status in breast cancer patients receiving neo-adjuvant chemotherapy (NACT).

Data was retrospectively collected for 88 patients between 2011 and 2016 from the hospital records. All patients had baseline MRI, followed by the end of neoadjuvant chemotherapy MRI. Patient demographics, cancer type, grade, stage, receptor status, and the number of positive lymph nodes identified on the baseline and preoperative MRI were recorded. The imaging results were compared to post-operative histopathological lymph node findings. The median patient age of the patients was 54 years (32–77 years)

There were 67 (76.1%) patients with histologically proven positive axillary lymph nodes on baseline MRI. The overall conversion from abnormal to normal axillary nodes following chemotherapy (ypN0) was 38.8% (26 patients out of 67). The sensitivity and specificity of MRI for predicting axillary status was 68.85 and 85.71%, respectively, with an overall MRI diagnostic accuracy of 73.07%.

MRI has low sensitivity and diagnostic accuracy in predicting axillary nodal status in breast cancer patients receiving neoadjuvant chemotherapy. Given the low NPV of MRI of the axilla, a negative MRI does not obviate the need for definitive axillary surgery.

In its current state, MRI cannot obviate the need for axillary surgery in patients receiving NACT. Long: short axis ratio (L: S) of the axillary lymph node is not a good predictor of axillary metastases.