ERBB2 and breast cancer: T1 and N-positive breast cancer occupied large proportion of patients in period I. The following characteristics were more commonly observed in period II than in period I: hormone receptor-negative (p = 0.001), HER-2-negative (p = 0.008), no adjuvant radiotherapy for initial breast cancer (p < 0.001), treated with adjuvant chemotherapy (p = 0.001), and treated with hormonal therapy (p < 0.001) (Table 2).