GSTP1 and breast cancer: Moreover, several combined variant genotypes among non-smokers were associated with a significantly reduced BC risk: GSTT1 null and GSTP1 Ile105Val + Val105Val (OR 0.07, 95 % CI 0.01–0.57; P = 0.01); GSTP1 Ile105Val + Val105Val and NRF2 −617CA + −617AA (OR 0.29, 95 % CI 0.08–0.98; P = 0.05); GSTT1 null and SOD2 Ala16Val + Val16Val (OR 0.14; 95 % CI 0.03–0.63; P = 0.01).