Therefore, the present study attempted to systematically evaluate the association between the ABCG2 G34A and C421A polymorphisms and the BC susceptibility, clinicopathological features, and clinical outcomes in BC patients after preoperative anthracycline-based NCT or postoperative anthracycline-, paclitaxel-, and anthracycline plus paclitaxel-based chemotherapy. Here, ABCG2 is linked to breast cancer.