Analysis of patterns of early or late recurrence-associated genes to define four distinct subgroups of breast cancer. (A) A total of 208 late recurrence-associated genes (P <0.0001) were selected for overall, early and late Cox regression survival analyses, and P values from three types of survival analyses are shown. (B) A total of 124 late recurrence-associated genes (P <0.0001) were selected for overall, early and late Cox regression survival analyses, and P value from these three types of survival analyses are shown. (C) Two-way hierarchical clustering (Centroid Linkage) of 216 probe sets that were significantly correlated with either early or late recurrence among 789 breast cancer samples, which included 743 lymph node-negative breast tumor samples obtained from patients who did not receive systemic neoadjuvant or adjuvant treatment, and 46 breast tumor epithelium samples for which gene expression of matched stromal tissue were available. Yellow boxes indicate upregulated gene cluster (C1 to C4) in related subgroups (G1 to G4). (D) Total, early or late recurrence-free survival was stratified according to breast cancer subgroups (G1 to G4). Tick marks in Kaplan-Meier estimates distant-metastasis-free survival indicate patients whose data were censored. P values were calculated using log-rank (Mantel-Cox) test.