Interaction between glutathione S-transferase M1-null/present polymorphism and adjuvant chemotherapy influences the survival of breast cancer.

Glutathione S-transferase M (GSTM) family is concerned with oxidative stress, which is associated with breast carcinogenesis and chemotherapy response. The null polymorphism of GSTM1 gene results in a thorough absence of the enzyme function. Our study was to evaluate the association between GSTM1 null/present polymorphism and chemotherapy treatment outcome in breast cancer patients. A total of unrelated 714 patients with a histologically confirmed breast cancer were randomly selected from two independent cancer centers. Polymerase chain reaction was performed to analyze null/present genotypes of GSTM1 in our study. Our study found that the present genotype of GSTM1 was associated with a better relapse-free survival (RFS) (P = .03) with adjusted hazard ratio (HR) [95% confidence interval (CI)] of 0.63 (95% CI: 0.42-0.93). The present genotype of GSTM1 was significantly correlated with a better RFS compared with the null genotype in the nonchemotherapy group (HR = 0.17, 95% CI: 0.06-0.50; P = 0.001), but no effect was observed in the chemotherapy group (HR = 0.81, 95% CI: 0.52-1.26; P = 0.35). Moreover, the interaction between the GSTM1-null/present genotype and adjuvant chemotherapy was significant (P = 0.04) in further analysis. Our study suggests that the GSTM1 polymorphism plays a complex role in influencing the chemotherapy response and breast cancer survival. It is suggested that the GSTM1-present genotype might prevent progression in breast cancer patients. In the meanwhile, it could damage the benefit of adjuvant chemotherapy as well in certain ways.