A decrease of colorectal cancer has been reported in users of menopausal hormone therapy;26 although a small increase was reported in ATAC (39 cases with anastrozole vs 31 with tamoxifen), a lower risk was seen in IBIS-II prevention (three with anastrozole vs 11 with tamoxifen), so the role of aromatase inhibitors in affecting risk of colorectal cancer remains uncertain. Here, CYP19A1 is linked to colorectal cancer.