GSTM1 and renal cell carcinoma: Although multiple subgroup analyses of geographic area, source of controls and quality scores revealed no association between the GSTM1 polymorphisms and RCC risk, the subgroup analysis of occupational exposure to pesticides showed a positive association between the GSTM1 polymorphisms and RCC risk (active+ exposure: P<0.05, OR = 3.44, 95% CI = 2.04–5.80; null+ exposure: P = 0.04, OR = 1.63, 95% CI = 1.02–2.57).