This is, to our knowledge, the first study in Egypt that evaluates the effect of SNPs in metabolic enzymes genes CYP2C19 (rs12248560) and ALDH3A1 (rs2228100), which play a role in the metabolism of cyclophosphamide drug in an AC regimen in female BC patients, along with SNPs in two transporter genes ABCB1 (rs1045642) and SLC22A16 (rs6907567), on the occurrence of adverse effects. This evidence concerns the gene SLC22A16 and breast cancer.