A study by Sharma et al (12) detected methylation of the glutathione S-transferase pi 1 (GSTP1) and breast cancer 1, early onset (BRCA1) genes in serum more frequently in non-responders to NAC than in responders, while Avraham et al (13) reported that none of the responders to NAC showed methylated Ras association (RalGDS/AF-6) domain family member 1 (RASSF1A) in the serum. Here, GSTP1 is linked to breast cancer.