XRCC4 and breast cancer: The MSH2, MLH1, PARP1, XRCC1, XRCC4, 53BP1, ERCC1, XPA of the metastasis group were higher than those of the control group (metastasis-free group) (P < 0.05), we can concluded that all of them are related to the prognosis of metastasis of breast cancer (Fig. 2).