Distant recurrence was reduced in the aromatase inhibitor group versus the tamoxifen group (RR 0·83, 95% CI 0·71–0·97; p=0·018; figure 1B, appendix p 4), but, with a median follow-up of 8·0 years, there was no significant difference in breast cancer mortality (1·01, 0·82–1·24; p=0·94; figure 1C) or all-cause mortality (1·04, 0·86–1·27; p=0·68; figure 1D, appendix p 6). Here, CYP19A1 is linked to breast cancer.