Jamieson et al. demonstrated that NQO2 rs1143684, missense Phe > Leu SNP, related to lower enzyme activity, modulates the adjuvant doxorubicin and cyclophosphamide (AC) efficacy and tamoxifen toxicity in 227 early breast cancer (BC) patients, with estrogen receptor (ER)- and progesterone receptor (PR)-negative disease [53]. This evidence concerns the gene PGR and breast cancer.