GSTM1 and renal cell carcinoma: So far, Ahmad et al. [40] have found that three-way combination of GSTM1-null, GSTT1-null and GSTP1-variant genotypes resulted in 4.5-fold increase in RCC risk, which is partially in agreement with our results, while Sweeny et al. [12] have shown an elevated risk of RCC in carriers of GSTT1-null genotype in all combinations of GSTM1 and GSTP1 genotypes.