Some treatments and prevention approaches leverage this cause by artificially reducing hormone levels, and thus discouraging hormone-sensitive cancers. Because steroid hormones are powerful drivers of gene expression in certain cancer cells, changing the levels or activity of certain hormones can cause certain cancers to cease growing or even undergo cell death.[1] Perhaps the most familiar example of hormonal therapy in oncology is the use of the selective estrogen-receptor modulator tamoxifen for the treatment of breast cancer. Another class of hormonal agents, aromatase inhibitors, now have an expanding role in the treatment of breast cancer.