Aromatase inhibitors are hormonal therapy medicines used to treat breast cancer and help stop breast cancer from coming back (recurrence) in postmenopausal women.
Research has shown that the aromatase inhibitor Aromasin (chemical name: exemestane) also can reduce the risk of first-time hormone-receptor-positive breast cancer in postmenopausal women at high risk for the disease.
Still, Aromasin is known to cause side effects and some women stop taking the medicine because of severe side effects, including muscle and joint pain.
A study has found that Aromasin had only a slight effect on quality of life for most women taking the medicine preventively.
The research was published online on April 21, 2014 by the Journal of Clinical Oncology. Read the abstract of “Quality of Life in MAP.3 (Mammary Prevention 3): A Randomized, Placebo-Controlled Trial Evaluating Exemestane for Prevention of Breast Cancer.”
Arimidex (chemical name: anastrozole) another aromatase inhibitor, also has been shown to reduce the risk of first-time hormone-receptor-positive breast cancer in postmenopausal women at high risk. Tamoxifen and Evista (chemical name: raloxifene), both SERMs (selective estrogen receptor modulators), another type of hormonal therapy medicine, also have been shown to reduce the risk of hormone-receptor-positive breast cancer in high-risk postmenopausal women. Tamoxifen also reduces the risk of hormone-receptor-positive breast cancer in high-risk premenopausal women.
Doctors call giving medicine to reduce the risk of a disease a person hasn’t been diagnosed with “prophylactic” or “preventive.”
While Aromasin and Arimidex haven’t been approved by the U.S. Food and Drug Administration to be used preventively for breast cancer, many doctors consider them good alternatives to tamoxifen or Evista. 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 Aromasin to reduce risk.
SERMs block the action of estrogen in breast and certain other cells by sitting in the cells' estrogen receptors. SERMs don't affect all estrogen receptors the same way because they're selective (as the name says). In bone cells, SERMs interact with the receptors the way estrogen does and strengthen bones. In breast cells, SERMs block the receptors' interaction with estrogen and limit cell growth.
Aromatase inhibitors work by stopping the body from producing estrogen, which limits the amount of estrogen available to stimulate hormone-receptor-positive breast cancer cells to grow.
The large MAP.3 trial was designed to see if Aromasin could reduce breast cancer risk in high-risk, undiagnosed postmenopausal women. Results released in February 2012 showed that Aromasin was effective, but didn’t really discuss any effects Aromasin had on the women’s quality of life.
For this latest report on MAP.3 results, the researchers assessed the quality of life of the 4,560 postmenopausal women in the MAP.3 trial. The women were split into two groups and randomly assigned to get either Aromasin or a placebo (a sugar pill). The women also were asked to fill out two surveys on quality of life issues that asked about:
- menopausal symptoms such as hot flashes and night sweats
- sexual problems, including vaginal dryness
- sleeping problems
- weight gain
- joint and muscle pain
- dry skin
The women completed the surveys before the study started, 6 months after the study started, and each year after that for the 5 years of the study.
Overall, 32% of the women taking Aromasin and 28% of the women taking the placebo stopped taking their medicine because of side effects. Hot flashes, joint pain, and fatigue were the top three reasons women in both groups gave for stopping treatment.
Compared to women taking the placebo pill, women who were taking Aromasin reported more hot flashes and night sweats in the first 6 months of the study. This difference became smaller as time went on.
Women younger than 60 reported having more severe hot flashes and night sweats compared to women older than 60.
Women taking Aromasin also said they had more joint pain than women taking the placebo. This difference was greatest 2 years after the study started.
There was no difference in pain levels between older and younger women.
Overall, the women reported that any side effects from Aromasin didn’t really affect their physical or mental health and didn’t stop them from working or participating in social activities.
While the results of this study are encouraging, they also may seem confusing to women taking Aromasin who have experienced severe side effects.
The researchers pointed out that several factors may have affected the results:
- Women with the most severe side effects were more likely to stop taking Aromasin early and so wouldn’t have been included in this longer follow-up.
- The questions on pain in one of the surveys may not have been sensitive enough to capture the severity of joint pain caused by Aromasin.
- Many of the studies done on the side effects caused by Aromasin have been done on women diagnosed with breast cancer who are taking Aromasin to treat breast cancer and reduce recurrence risk. The MAP.3 trial involved women at high-risk but not diagnosed. There may be a difference in the effects of Aromasin on women who’ve been diagnosed with breast cancer and women who haven’t.
If you’re a postmenopausal woman with a higher-than-average risk of breast cancer, you already may be taking medicine to help keep your risk as low as it can be. If not, you may want to ask your doctor if taking tamoxifen, Evista, Arimidex, or Aromasin makes sense for you. If you’re taking one medicine and having unacceptable side effects, talk to your doctor about switching to a different medicine. And always ask your doctor about the benefits and risks of any treatment you’re considering. Together, you can make the best choice for your unique situation.
You can learn more about Aromasin, Arimidex, tamoxifen, and Evista in the Breastcancer.org Hormonal Therapy section.