HPGDS and renal cell carcinoma: During the selection process, 49 studies were removed: 18 studies were duplicate studies; 23 studies were not available in full text or did not show a correlation between the three GSTs genotype (GSTM1, GSTT1 and GSTP1) polymorphisms and risk of RCC; 3 studies were reviews; 3 studies were not case-control studies; 1 did not provide any useful data; and 1 studie provided the same data as another included one.