Our study showed that the ERCC1 expression in patients with breast cancer treated with trastuzumab had no significant correlation with age at diagnosis, menopausal status, tumor size, vascular tumor thrombus, pathological type, PR, Ki-67, lymph node metastasis (P > 0.05), but significant correlations were observed among ERCC1, chemotherapy and ER repression (P < 0.05). This evidence concerns the gene ESR1 and breast cancer.