Women Who Have Aromatase Inhibitor Side Effects Before Starting Medicine Less Likely to Finish Therapy

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After surgery, women diagnosed with hormone-receptor-positive breast cancer usually take hormonal therapy medicine to reduce the risk of the cancer coming back (recurrence). Hormonal therapy medicines work in two ways:

  • by lowering the amount of estrogen in the body
  • by blocking the action of estrogen on breast cancer cells

There are several types of hormonal therapy medicines. Tamoxifen, a selective estrogen receptor modulator (SERM), is one of the most well-known. Tamoxifen can be used to treat both premenopausal and postmenopausal women. In 2005, the aromatase inhibitors:

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

were shown to be more effective at reducing recurrence risk in postmenopausal women and are now used more often than tamoxifen to treat women who’ve gone through menopause. Aromatase inhibitors aren’t used to reduce recurrence risk in premenopausal women.

Both tamoxifen and aromatase inhibitors can cause side effects. Tamoxifen may cause hot flashes and increase the risk of blood clots and stroke. Aromatase inhibitors may cause muscle and joint aches and pains. Less common but more severe side effects of aromatase inhibitors are heart problems, osteoporosis, and broken bones. Research has shown that about 25% of women who are prescribed hormonal therapy to reduce the risk of recurrence after surgery either don’t start taking the medicine or stop taking it early.

A study has found that women who are having side effects commonly associated with aromatase inhibitors BEFORE they start taking an aromatase inhibitor are much more likely to stop taking the medicine early.

The study, “Associations between baseline patient-reported symptoms and discontinuation of adjuvant aromatase inhibitor (AI) therapy,” was presented on Dec. 12, 2013 at the 2013 San Antonio Breast Cancer Symposium.

Treatment that comes after surgery or another initial treatment is called adjuvant treatment. Adjuvant treatment is given to increase the chances that the cancer will not come back.

In the study, the researchers randomly assigned 503 postmenopausal women who had been diagnosed with early-stage estrogen-receptor-positive breast cancer to take either Aromasin or Femara for 2 years. The women were about 59 years old, overweight, and most had received chemotherapy and taken tamoxifen before starting the study.

Before the women started taking either Aromasin or Femara as part of the study, the researchers asked them questions about their:

  • sleep quality
  • moods
  • ability to think and concentrate
  • fatigue level
  • joint pain

The researchers asked the same questions 1, 3, 6, 12, and 24 months after the women started taking the aromatase inhibitor.

About one-third (142) of the women stopped taking the aromatase inhibitor either before or by 12 months because of unacceptable side effects.

The top three reasons the women gave for stopping either Aromasin or Femara were:

  • poor sleep
  • fatigue
  • forgetfulness

The researchers found that women who stopped taking the aromatase inhibitor early were more likely to have three to five of the side effects BEFORE they started taking the aromatase inhibitor.

It’s worth noting that while joint pain is a common side effect of the aromatase inhibitors, in this study it wasn’t a top reason why women stopped taking the medicine early.

If you’re a postmenopausal woman who’s been diagnosed with hormone-receptor-positive, early-stage breast cancer and will be taking an aromatase inhibitor after surgery and other treatments, it’s very important that you take the medicine for as long as it’s prescribed. Hormone-receptor-positive breast cancer can come back and hormonal therapy after surgery reduces that risk -- you must remember that.

Side effects caused by aromatase inhibitors can be very troublesome for many women. It’s important to talk to your doctor as soon as you start having any side effects common to aromatase inhibitors, including trouble sleeping, fatigue, or difficulty concentrating, even if you haven’t started taking an aromatase inhibitor yet. Don’t wait until the symptoms are intolerable and you have to stop taking the medicine. There are steps you can take to ease these side effects, including switching to a different type of hormonal therapy.

For more information, visit the Breastcancer.org pages on Staying on Track With Treatment. You can read about why it’s so important to stick to your treatment plan, as well as ways to manage side effects after radiation, chemotherapy, and hormonal therapy. If you’re taking hormonal therapy after surgery now, stick with it as prescribed. If you’re thinking of stopping early, talk to your doctor first. Together, you can find a solution that is best for you.


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