A study found that postmenopausal women with a higher-than-average risk of breast cancer who took the hormonal therapy Aromasin (chemical name: exemestane) reduced their risk of breast cancer by 65% compared to women who took a placebo (sugar pill).
The results were published in the New England Journal of Medicine and presented at the American Society of Clinical Oncology (ASCO) annual meeting.
Right now, Aromasin is not approved by the U.S. Food and Drug Administration (FDA) to be used to reduce breast cancer risk in high-risk women.
Two other hormonal therapy medicines, tamoxifen (brand name: Nolvadex) and Evista (chemical name: raloxifene), are FDA-approved to lower breast cancer risk in postmenopausal women with higher-than-average risk but haven't been diagnosed. Research has found that tamoxifen and Evista can lower breast cancer risk in high-risk postmenopausal women by about 50%. Tamoxifen also is approved to reduce breast cancer risk in high-risk PREmenopausal women who haven't been diagnosed.
Both tamoxifen and Evista are selective estrogen receptor modulators (SERMs). SERMs block the effects of estrogen in the breast tissue. SERMs work by sitting in the estrogen receptors in breast cells. If a SERM is in the estrogen receptor, there is no room for estrogen and it can't attach to the cell. If estrogen isn't attached to a breast cell, the cell doesn't receive estrogen's signals to grow and multiply.
Aromasin is an aromatase inhibitor hormonal therapy medicine. Other aromatase inhibitors are:
- Arimidex (chemical name: anastrozole)
- Femara (chemical name: letrozole)
Aromatase inhibitors stop the production of estrogen in postmenopausal women. Aromatase inhibitors work by blocking the enzyme aromatase, which turns the hormone androgen into small amounts of estrogen in the body. This means that less estrogen is available to stimulate the growth of hormone-receptor-positive breast cancer cells.
Aromatase inhibitors are given:
- after surgery and other treatments to lower the risk of early-stage, hormone-receptor-positive breast cancer coming back (recurrence)
- to treat hormone-receptor-positive advanced-stage breast cancer
Aromatase inhibitors can't stop the ovaries from making estrogen, so aromatase inhibitors only work in postmenopausal women.
All the aromatase inhibitors are pills taken by mouth.
In this study, postmenopausal women at high risk who took Aromasin lowered their breast cancer risk by 65%. This is more than the 50% risk reduction offered by tamoxifen and Evista. So it's possible that doctors will consider Aromasin as a good alternative to tamoxifen or Evista to reduce breast cancer risk in high-risk postmenopausal women who've never been diagnosed with breast cancer. The FDA also may consider approving Aromasin for this use.
It's important to know that Aromasin can reduce breast cancer risk in high-risk, POSTmenopausal women only. The study didn't look at using Aromasin in PREmenopausal women.
Both SERMs and aromatase inhibitors have side effects, including some that are serious:
- Hot flashes and night sweats (vasomotor symptoms) are side effects of SERMs and aromatase inhibitors, but more common with SERMs.
- Joint pain is more common with aromatase inhibitors.
- SERMs or aromatase inhibitors can cause dangerous blood clots in rare cases; this is more common with SERMS.
- Aromatase inhibitors can weaken bones and make it more likely to break a bone.
If you're a postmenopausal woman with a higher-than-average risk of breast cancer, ask your doctor about steps you can take to help lower your risk. Hormonal therapy may be an option you and your doctor consider. If so, you may want to discuss this study and ask if Aromasin might be a good choice for you. If you do decide to take hormonal therapy medicine as part of your risk reduction plan, ask your doctor about the benefits and side effects of each one and keep two things in mind:
- Every woman responds differently to treatment. The benefits and risks of each option should be compared.
- Your treatment plan isn't written in stone. You can always switch medicines if another treatment offers the potential for greater benefit and/or fewer side effects.
Visit the Breastcancer.org Lower Your Risk section to learn more about the steps you can take to help keep your breast cancer risk as low as it can be.
Editor's Note: In July 2013, the American Society of Clinical Oncology put out new guidelines on using hormonal therapy medicines to reduce breast cancer risk in high-risk undiagnosed women. Besides tamoxifen and Evista, the guidelines also recommend that doctors talk to postmenopausal high-risk women about using the aromatase inhibitor Aromasin (chemical name: exemestane) to reduce risk.