In the second 5 years after BC diagnosis, none of the HRs for having family history was significant among the full cohort (HR, 1.03; 95% CI, 0.87-1.23), the ER-positive subgroup (HR, 1.05; 95% CI, 0.86-1.29), or the ER-negative subgroup (HR, 1.00; 95% CI, 0.65-1.53). This evidence concerns the gene ESR1 and breast cancer.