First, the sample size was much larger, with 88 studies involving 28,676 BC cases and 32,539 controls assessed for the GSTM1 null genotype, 67 studies involving 23,092 BC cases and 26,381 controls for the GSTT1 null genotype, and 56 studies involving 25,331 BC cases and 27,424 controls in all populations. This evidence concerns the gene GSTM1 and breast cancer.