Aromatase inhibitor therapy involves medications that reduce estrogen levels by blocking the aromatase enzyme. This enzyme is responsible for estrogen production, so inhibiting it lowers the amount of estrogen available. This treatment is a form of hormone therapy.
Purpose of Aromatase Inhibitors
Aromatase inhibitors are primarily prescribed for hormone receptor-positive breast cancer, especially in postmenopausal women. This cancer relies on estrogen to grow, so reducing estrogen levels can slow or stop tumor growth.
The therapy is used in several contexts. In the adjuvant setting, it is given after initial treatments like surgery to reduce the risk of cancer returning. For metastatic breast cancer, aromatase inhibitors manage the disease.
Premenopausal women with hormone receptor-positive breast cancer may also receive aromatase inhibitors if combined with ovarian suppression therapy, which temporarily stops the ovaries from producing estrogen. Aromatase inhibitors may also be considered for men with breast cancer.
How Aromatase Inhibitors Work
Aromatase inhibitors function by targeting the aromatase enzyme, which is responsible for converting other hormones, specifically androgens, into estrogens. In postmenopausal women, where the ovaries no longer produce estrogen, peripheral tissues like fat, muscle, and breast tissue become the main sources of estrogen production through this aromatase activity.
There are two main types of aromatase inhibitors: steroidal and non-steroidal. Steroidal inhibitors, such as exemestane, bind irreversibly to the aromatase enzyme, deactivating it permanently. Non-steroidal inhibitors, including anastrozole and letrozole, bind reversibly to the enzyme, competitively blocking its ability to produce estrogen.
Administering Aromatase Inhibitors and Managing Side Effects
Aromatase inhibitors are administered as oral pills, taken once daily. It is recommended to take the medication around the same time each day, and tablets should be swallowed whole.
The duration of treatment varies. For early-stage breast cancer, it ranges from 5 to 10 years, either as initial therapy or following tamoxifen treatment. For advanced or metastatic breast cancer, treatment continues until the disease progresses. Healthcare providers determine the specific duration based on individual patient factors and cancer characteristics.
Common side effects resemble menopausal symptoms due to estrogen reduction. These include hot flashes, joint and muscle aches or stiffness, and vaginal dryness. Other side effects include fatigue, headaches, and gastrointestinal symptoms.
To manage joint and muscle pain, regular exercise, pain relievers, and applying heat or cold are helpful. Hot flashes can be alleviated by dressing in layers, avoiding triggers, and using cooling techniques. For bone density changes, which can lead to osteoporosis and fractures with long-term use, healthcare providers recommend vitamin D and calcium supplements, along with regular bone density monitoring through DEXA scans.