GSTM1 and breast cancer: Recent two meta-analyses involving 26 (Zhang et al. 2011b) and 33 (Jiang et al. 2011) studies showed that GSTM1 homozygous deletion was found to slightly influence BC risk in Caucasians and Asians, while in Africans the influence of GSTM1 null genotype on cancer risk was not observed.