Preoperative axillary nodal staging with ultrasound and magnetic resonance imaging: Predictive values of quantitative and semantic features

Objective: Although axillary imaging has recently received renewed interest for preoperative staging in tandem with the evolving minimally invasive surgical approaches, axillary imaging is limited by the lack of standardization in the interpretation. We aimed to classify imaging features in ultrasound and MRI into quantitative and semantic features and evaluate predictive value of each feature for predicting nodal metastases. Methods: A total of 316 breast cancers patients who underwent ultrasound and MRI prior to axillary surgery were included. Retrospective reviews of our breastimaging database were done for the quantitative features [cortical thickness (CT) and CT-derived parameters, long diameter (LD), short diameter (SD), and LD/SD ratio] and semantic features (eccentricity, loss of fatty hilum, and irregularity) of the axillary lymph node in images. Odd ratios (ORs) for each imaging feature were calculated with adjustment for clinicopathological characteristics significantly associated with nodal metastases. Results: All CT-derived parameters were significantly associated with nodal metastases in both ultrasound and MRI (OR, 3.3-3.5 for ultrasound and 3.3-3.9 for MRI, respectively; Ps < .05). For the ultrasound, LD/SD ratio (OR, 2.1), eccentricity (OR, 2.4), and fatty hilum loss (OR, 27.2) were significantly associated with nodal metastases (Ps < .05). For the MRI, SD (OR, 2.1) and eccentricity (OR, 3.0) were significantly associated with nodal metastases (Ps < .05). Conclusion: Among the quantitative features, all CT-derived parameters can be used for predicting nodal metastases. Significant predictors of semantic features were heterogeneous between ultrasound and MRI. Advances in knowledge: (1) Imaging features of ultrasound and MRI for preoperative axillary nodal staging can be classified into quantitative and semantic features. (2) Predictive values of each imaging features are heterogeneous for predicting nodal metastases.