The multivariable hazard ratios and 95% confidence intervals of breast cancer death were 0.92 (95% CI = 0.88 to 0.97) for each additional calendar year of diagnosis, 4.38 (95% CI = 2.79 to 6.87) for grade 3 vs grade 1 tumors, 0.43 (95% CI = 0.31 to 0.62) for progesterone receptor–positive vs progesterone receptor–negative disease, and 2.01 (95% CI = 0.99 to 4.07) for HER2-positive vs HER2-negative disease. This evidence concerns the gene PGR and breast cancer.