ESR1 and breast cancer: Using multiple SNPs obtained from blood, there was evidence of protective association with overall (OR per SD increase in expression level: 0.96; 95% CI 0.93, 0.99; P = 0.01) and ER+ breast cancer (OR per SD increase in expression level: 0.94; 95% CI 0.91, 0.98; P = 0.001) consistent to single SNP analyses.