Glutathione S-transferase M1 and T1 polymorphism and response to neoadjuvant chemotherapy (CAF) in breast cancer patients.

Purpose: Response to neoadjuvant chemotherapy (NACT) for breast cancer patients cannot be predicted; however, polymorphism of the glutathione S-transferase genes GSTM1 and GSTT1 can modify the response to chemotherapy. The aim of this study was to establish whether there is an association between the polymorphism of GSTM1 and GSTT1 and response to NACT.

Methods: The subjects of this study were 45 patients with locally advanced breast cancer (LABC), who received the cyclophosphamide, adriamycin, and 5-fluorouracil (CAF) regimen as NACT. We analyzed the relationship between the genotypes and responses to chemotherapy.

Results: The response rates to chemotherapy were better, although not significantly so, in patients with the GSTM1 and GSTT1 null genotypes (odds ratio [OR] 2.06 and 1.45). Similar findings were noted in patients with either or both of the null genotypes (OR 2.67 and 1.16). Among the responders, patients with the GSTM1 and GSTT1 null genotypes had higher rates of complete response following chemotherapy than those with one or more active allele (OR 1.8 and 1.3), although the difference was not significant.

Conclusions: There was an association between the polymorphism of glutathione S-transferases and responses to chemotherapy, but the differences were not significant. However, larger studies are needed to investigate the role and efficiency of GST polymorphism in predicting response to chemotherapy.