GSTM1 and cancer: In the subgroup analysis by ethnicity, the results indicated that individuals with GSTM1 null genotype had a significantly higher cancer risks among Caucasians (null vs. present: OR = 1.14, 95%CI = 1.09–1.18, p<0.001), Asians (null vs. present: OR = 1.26, 95%CI = 1.19–1.33, p<0.001) and the mixed descendants (null vs. present: OR = 1.12, 95%CI = 1.03–1.23, p<0.001), but not for Africans (null vs. present: OR = 0.93, 95%CI = 0.77–1.12, p = 0.42).