ROC curve for LNM. Receiver operating characteristic (ROC) curve for lymph node metastasis with 5-fold cross-validation SVM models and radiologist. The AUC of k1 to k5 SVM models were 0.862, 0866, 0.878, 0.900 and 0876, respectively. Compared with the radiologist, the P values were all less than 0.05 (Table 3). For the five SVM models, the mean of AUCs was 0.876. And the AUC of radiologist based LN size was 0.757.