Multimodal radiomics and nomogram‐based prediction of axillary lymph node metastasis in breast cancer: An analysis considering optimal peritumoral region

Abstract Purpose To explore the optimal peri‐tumoral regions on ultrasound (US) images and investigate the performance of multimodal radiomics for predicting axillary lymph node metastasis (ALNM). Methods This retrospective study included 326 patients (training cohort: n = 162, internal validation cohort: n = 74, external validation cohort: n = 90). Intra‐tumoral region of interests (ROIs) were delineated on US and digital mammography (DM) images. Peri‐tumoral ROI (PTR) on US images were gained by dilating actual 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 mm radius surrounding the tumor. Support vector machine (SVM) method was used to calculate the importance of radiomics features and to pick the 10 most important. Recursive feature elimination‐SVM was used to evaluate the efficacy of models with different feature numbers used. Results The PTR 0.5mm yielded a maximum AUC of 0.802 (95% confidence interval (CI): 0.676–0.901) within the validation cohort using SVM classifier. The multimodal radiomics (intra‐tumoral US and DM and US‐based PTR 0.5mm radiomics model) achieved the highest predictive ability (AUC = 0.888/0.844/0.835 and 95% CI = 0.829–0.936/0.741–0.929/0.752–0.896 for training/internal validation/external validation cohort, respectively). Conclusion The PTR 0.5mm could be the optimal area for predicting ALNM. A favorable predictive accuracy for predicting ALNM was achieved using multimodal radiomics and its based nomogram.