Diagnostic Accuracy of Pre-Operative Breast Magnetic Resonance Imaging (MRI) In Predicting Axillary Lymph Node Metastasis: Variations In Intrinsic Subtypes, And Potential to Omit Sentinel Lymph Node Biopsy In Some Low Risk Groups of Patients With Invasive Breast Cancer. 

Abstract Purpose: The value and utility of axillary lymph node(ALN) evaluation with MRI in breast cancer were not clear for various intrinsic subtypes. The potential of breast MRI to identify low risk groups for which is feasible to omit sentinel lymph node biopsy (SLNB) was evaluated according to the ACOSOG Z0011 trial.Methods: Patients with primary operable breast cancer with pre-operative breast MRI and post-operative pathologic reports were retrospectively collected. The concordance of MRI and pathology of ALN status was analyzed in different intrinsic subtypes. Furthermore, our rationale to omit SLNB in the low risks group was validated in a cohort of patients from the Taiwan Cancer Registry (TCR) by comparing locoregional events, distant metastasis, and survival outcomes.Results: A total of 1560 patients were enrolled. The overall accuracy and negative predictive value (NPV) of breast MRI to predict the ALN metastasis are 69.6% and 80.6%. Accuracy, sensitivity, specificity, NPV, and PPV of MRI in detecting metastatic ALN are all significantly different between intrinsic subtypes (p<0.05). Multivariate analysis identified tumor size and histologic type as independent predictive factors of ALN metastases. Patients with a pre-operative breast MRI node-negative status along with a tumor size ≤ 2 cm and intrinsic subtype of Luminal A, Luminal B1, or TNBC were potential candidates to omit SLNB. In a cohort of 19,620 patients with clinical node-negative status and tumor size ≤ 2cm(cT1N0M0) from the TCR database, there were not significant differences between those with or without ALN surgery in terms of locoregional recurrence, distant metastasis free survival, and overall survival after BCS and radiotherapy.Conclusion: The diagnostic accuracy of MRI to predict ALN metastasis varied according to intrinsic subtype. Combined pre-operative clinicopathologic and MRI findings might identify some low risk groups of invasive breast cancer patients who are potentially suitable to omit SLNB.