The goal of hormonal therapies is to stop steroids from stimulating cancer growth, in other words, to starve the tumor. Aromatase inhibitors act by blocking the conversion of steroid precursors (mostly androgens) to their active form (usually estradiol) by inhibiting the aromatase enzyme.
Anti-aromatase drugs (anastrozole, letrozole and exemestane) are a class of hormonal agents that work by inhibiting the formation of estrogen in the body, thereby reducing the exposure of the hormone-sensitive tumor to estrogen. By inhibiting the enzyme aromatase, these drugs block the conversion of estrogens into their active form and reduce levels of active estrogen in the body. The graphic below depicts the biosynthesis of estrogens and the role of aromatase.
Anti-aromatase drugs have thus far proven to cause different side effects than tamoxifen. Main adverse effects are postmenopausal symptoms (hot flushes, increased perspiration, osteoporosis, arthralgia etc.) due to estrogen deprivation. It can be wise to add bisphosphonates in order to decrease the risk on osteoporosis.
They are now used as a first-line treatment for metastatic disease in postmenopausal women.