The 5-year absolute risk of breast cancer recurrence was 3·2% (95% CI 1·8–4·5) lower in the aromatase inhibitor group than in the tamoxifen group (6·9% vs 10·1%, figure 1A), with a similar absolute difference in 10-year recurrence: 14·7% in the aromatase inhibitor group versus 17·5% in the tamoxifen group. This evidence concerns the gene CYP19A1 and breast cancer.