ESR1 and neoplasm: The major differences compared with the results from the main analysis were that the association between tumor grade and BCD was attenuated (3 vs 1: HR = 1.65, 95% CI = 0.87 to 3.11 in the simple model and HR = 2.60, 95% CI = 1.02 to 6.61 in the full model) and that ER positivity vs ER negativity was associated with a higher, not lower, risk of BCD (ER+ vs ER-: HR = 1.55, 95% CI = 1.06 to 2.27 in the simple model and HR = 1.96, 95% CI = 0.79 to 4.86 in the full model).