ESR1 and breast carcinoma: For in situ cancer, based on 255 ER+ cases, risk of ER+ breast cancer was significantly elevated for recent OC use (OR = 1.66, 95% CI = 1.02 to 2.68), but was not associated with long duration of OC use (OR = 0.95, 95% CI = 0.51 to 1.75).