GSTM1 and urinary bladder cancer: Although in meta-analysis (Jiang et al. 2011) the effect of GSTM1 null genotype on BC risk was increased by smoking habit, the joint effect of GSTM1 null genotype was not greater among smokers, never and former smokers in the present study, as well as in New England bladder cancer study (Moore et al. 2011).