IGF1R and breast carcinoma: This retrospective NHS2 cohort study in largely White non-Hispanic women validates earlier CTS findings and confirms that women with preeclampsia who have inherited the common T allele of IGF1R rs2016347 have a 30–40% lower risk of developing HR+ breast cancer, pointing to the need to consider incorporating this exposure information (preeclampsia history and IGF1R rs2016347 genotyping) into risk assessment models and personalized breast cancer screening recommendations.