Aromatase Inhibitors Increase Risk of Heart Problems

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Hormonal therapy medicines are used to treat hormone-receptor-positive breast cancer. Aromatase inhibitors and tamoxifen are two types of hormonal therapy.

A study found that women diagnosed with early-stage, hormone-receptor-positive breast cancers who were treated with an aromatase inhibitor were 26% more likely to have cardiac problems -- heart attack, heart-related chest pain (angina), or heart failure -- compared to women treated with tamoxifen. These results were presented at the 2010 San Antonio Breast Cancer Symposium (SABCS).

Many postmenopausal women take hormonal therapy -- either an aromatase inhibitor or tamoxifen -- after surgery and other treatments for hormone-receptor-positive, early-stage breast cancer. Hormonal therapy reduces the risk of the cancer coming back (recurrence). Hormonal therapy used in this way is called adjuvant hormonal therapy.

The aromatase inhibitors are:

  • Arimidex (chemical name: anastrozole)
  • Aromasin (chemical name: exemestane)
  • Femara (chemical name: letrozole)

In many cases, one hormonal therapy medicine -- tamoxifen or an aromatase inhibitor -- is taken for 5 years. This is called monotherapy. In other cases, women take tamoxifen for 2 or 3 years and then switch to an aromatase inhibitor until the hormonal therapy has been taken for a total of 5 years. So you might take tamoxifen for 2 years and an aromatase inhibitor for 3 years. This is called sequential therapy.

Researchers analyzed the results of seven large studies that looked at the benefits and risks of hormonal therapy medicines:

  • Five years of an aromatase inhibitor is somewhat better than 5 years of tamoxifen for reducing the risk of recurrence in postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer -- about 20% better overall.
  • Sequential therapy (tamoxifen for 2 to 3 years followed by an aromatase inhibitor) can reduce the risk of recurrence about the same as 5 years of an aromatase inhibitor.

The risk of cardiovascular problems is low with either type of hormonal therapy, but this analysis found that the risk of cardiovascular problems was 26% higher in women taking an aromatase inhibitor:

  • 3.4% of the women treated with 5 years of tamoxifen had a cardiovascular problem compared to 4.2% of the women treated with 5 years of an aromatase inhibitor.
  • Women who got tamoxifen for 2 to 3 years followed by an aromatase inhibitor had the same risk of cardiovascular problems as women who got 5 years of tamoxifen.

In rare cases, both tamoxifen and the aromatase inhibitors can lead to dangerous blood clots. This risk is higher with tamoxifen and lower with an aromatase inhibitor.

Both tamoxifen and the aromatase inhibitors have been linked to a small risk of uterine cancer. This risk is higher with tamoxifen and lower with an aromatase inhibitor.

The aromatase inhibitors can weaken bones and make women more likely to break a bone, though this is uncommon. Tamoxifen actually can strengthen bones. This study found that broken bones due to hormonal therapy were 47% more likely in women who got 5 years of an aromatase inhibitor compared to women who got 5 years of tamoxifen.

Research also has shown that hot flashes and night sweats -- called vasomotor symptoms -- are side effects of both tamoxifen and the aromatase inhibitors, though they're more common with tamoxifen. Joint pain is a more common side effect of the aromatase inhibitors.

If you're a postmenopausal woman diagnosed with hormone-receptor-positive, early-stage breast cancer, keep two things in mind when you and your doctor are deciding on an adjuvant hormonal therapy plan:

  • Every woman responds differently to treatment. What works for someone else may not work for you and what works for you may not work for someone else.
  • Your treatment plan isn't written in stone. You can always switch medicines if another treatment has greater benefits and/or fewer side effects.

Ask your doctor about the benefits and risks of aromatase inhibitors and tamoxifen for your unique situation, as well as the pros and cons of monotherapy compared to sequential therapy.

Based on the results of this study, tamoxifen monotherapy or sequential hormonal therapy (tamoxifen for 2 to 3 years followed by an aromatase inhibitor) may be a better approach for you if you have heart problems, or at high risk for heart problems.

Together, you and your doctor can decide on a treatment plan that's best for YOU.

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