ERBB2 and breast cancer: Since the 2017 V3 version of the NCCN breast cancer guidelines for the first time added the PARP inhibitor olaparib as a treatment option for patients with HER-2 negative BRCA1/2 (members of the HRR pathway) mutations (16), the significance of the DDR gene (including the HRR gene) in the guidance of therapy has attracted more and more attention, including multiple directions of chemotherapy, targeted therapy, and immunotherapy.