Following treatment with NAC and prior to surgery, serum samples obtained from 120 patients with stage II/III breast cancer were subjected to the OS-MSP assay for analysis of the glutathione S-transferase pi 1, Ras association (RalGDS/AF-6) domain family member 1 and retinoic acid receptor β2 genes. This evidence concerns the gene GSTP1 and breast carcinoma.