CYP19A1 and cancer: These deaths were distributed across several second primary cancer sites: lung (six in the aromatase inhibitor group vs four in the tamoxifen group), ovarian (four vs one), pancreatic (four vs one), haematological (three vs one), and other specified sites (five vs three), and there was no difference in the overall incidence of fatal or non-fatal second cancers (RR 1·08, 95% CI 0·84–1·40; p=0·55; appendix p 16).