GSTM1 and breast cancer: However, when we restrained only high-quality studies, HWE, matching, and genotyping examination performed blindly or with quality control, significantly increased BC risk was found in the overall analysis for GSTM1 null genotype, all populations, Caucasians, and postmenopausal women for the combined effects of GSTM1 and GSTT1 polymorphisms, and overall analysis for the combined effects of GSTM1, GSTT1, and GSTP1 IIe105Val polymorphisms.