GSTM1 and cancer: Finally, 85 articles (19,604 cases and 23,710 controls) were kept (Fig. 1), of which 70 articles (16,131 cases and 19,696 controls) were about the relationship between GSTM1 and cancers[4,5,16,17,24–89] (Table 1); 49 articles (11,555 cases and 14,606 controls) were about the relationship between GSTT1 and cancers[4,5,16,24,25,27–31,33,34,36–39,41,42,44–49,51,52,56,58,60,61,63,65–68,70,74–76,79,80,82–85,87,88,90–93] (Table 2); and 31 articles (8518 cases and 9884 controls) were about GSTP1 and cancers[5,16,17,24,30,31,34,36,42,44,45,47,49,52,59,66,67,70,79,88,94–103] (Table 3) among smokers.