As an example, the marker rs10235235 observed at the CYP3A locus15 has MAF 0.09 in women of European ancestry and odds ratios for breast cancer of 0.979 (95% CI: 0.915–1.047) and 0.906 (95% CI: 0.864–0.950) in women with age at menarche ≤12 years and >12 years, respectively. This evidence concerns the gene CYP3A4 and breast cancer.