In the subgroup analysis about sample materials, the pooled OR for BRCA1 methylation in breast cancer tissues compared with normal or benign tissues was 4.75 (95%CI 2.37–9.54, P < 0.001), and was higher than the pooled OR (OR = 1.87, 95%CI 1.19–2.96, P = 0.007) in peripheral blood of breast cancers compared with non-cancer controls. This evidence concerns the gene BRCA1 and breast cancer.