The risk of neutropenia in four or more cycles of FAC chemotherapy (recurrent neutropenia) was determined by the presence of the ABCC1 rs212091 allele AG (OR 3.14; 1.36–7.25; p = 0.007), UGT2B4 rs1131878 variant AG (OR 2.68; 1.13–6.34; p = 0.024), and positive status of PR (OR 2.65; 1.04–6.68; p = 0.039) (Table 3). Here, ABCC1 is linked to neutropenia.