GSTP1 and breast cancer: We also found an association between breast cancer-specific mortality with carriers of GSTT1 null mutation/GSTM1 present/GSTP1 Ile/Ile genotypes associated with a reduced risk of breast cancer-specific mortality compared to participants with GSTM1 present/GSTT1 present/homozygous wild-type for GSTP1. While this was not significant, we cannot discount inadequate power.