CYP19A1 and breast cancer: It was also shown that in patients with early stage, hormone-sensitive BC who were receiving therapy with aromatase inhibitors, the OPG SNP rs2073618 plus the RANKL SNP rs7984870 were associated with aromatase inhibitor-related musculoskeletal adverse events, a finding thought to be mediated by an increased RANKL/OPG ratio, higher levels of serum biomarkers of bone turnover, and a lower lumbar spine BMD [19].