Performance of the core gene set in classification and survival analysis. (A) A receiver operating characteristic (ROC) curve for the Random Forest classification of metastatic versus non-metastatic samples in the van de Vijver dataset using the genes of the core gene set whose expression significantly differed between metastatic and non-metastatic samples in the van de Vijver dataset (Wilcoxon rank-sum, FDR < 0.01) as the features. (B) Patients from the van de Vijver dataset with a positive GSAS for the core gene set (red curve) show significantly shorter survival times than those with a negative GSAS (green curve). Vertical hash marks indicate points of censored data. (C) In a Cox PH model, the GSAS for the core gene set significantly predicts patient survival even after adjusting for traditional clinical features. (D) The core gene set is effective in predicting patient survival in ER+ samples but not in ER- samples.