Intra- and inter-reader agreement of the Node-RADS v1.0 score for axillary lymph node assessment on preoperative breast MRI.

PURPOSE: To assess intra- and inter-reader agreement of the Node-RADS v1.0 score for axillary lymph node evaluation in breast cancer (BC) patients undergoing preoperative breast MRI (bMRI), and to explore its patient-level association with pathological nodal involvement. Contrast-enhanced CT was evaluated as a subgroup exploratory analysis.

METHODS

This retrospective study included 100 women with biopsy-proven BC who underwent preoperative bMRI; 25 also underwent contrast-enhanced CT. Four readers (two expert breast radiologists and two junior readers) independently assigned Node-RADS v1.0 scores to the most suspicious axillary lymph node on MRI (n = 100) and CT (n = 25). Thirty bMRI examinations were re-evaluated after a 3-week washout to assess intra-reader agreement. Agreement was assessed using percent agreement and quadratic-weighted Cohen's κ. Exploratory patient-level diagnostic performance for pathological nodal involvement was evaluated using ROC analysis and AUC values.

RESULTS

Inter-reader agreement on bMRI was moderate among junior readers (κ = 0.59; 95%CI: 0.39-0.79) and almost perfect among expert readers (κ = 0.98; 95%CI: 0.96-1.00). Intra-reader agreement ranged from substantial to almost perfect. Diagnostic performance on bMRI was moderate for most readers (AUC 0.62-0.64), with higher AUC in one junior reader (AUC 0.79). In the clinically selected CT subgroup, AUC values ranged from 0.74 to 0.90. A Node-RADS threshold >2 showed the most balanced sensitivity-specificity trade-off in this cohort.

CONCLUSION

Node-RADS v1.0 showed good to excellent reproducibility for axillary lymph node assessment, particularly among expert readers. Diagnostic performance was exploratory and variable, reflecting the patient-level reference standard and the one-node-per-axilla approach. A Node-RADS threshold >2 may represent a pragmatic exploratory cut-off for patient-level risk stratification.