Women who had used COC for 10 years or longer had a slightly higher OR of ER- PR- breast cancer (OR 1.27, 95% CI 0.75 to 2.14) but a lower OR of ER+PR+ breast cancer (OR 0.76, 95% CI 0.49 to 1.18) compared with never users. This evidence concerns the gene ESR1 and breast cancer.