Exercise Helps Ease Aromatase Inhibitor Side Effects

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Much research has shown that exercise, a healthy diet, and counseling can help women feel better physically and emotionally, both during and after breast cancer treatment.

A study has found that exercise eases some of the side effects that may be caused by aromatase inhibitors, particularly weight gain, which improves body composition.

The research was published online on Dec. 27, 2017 by the journal Obesity. Read the abstract of “The effect of exercise on body composition and bone mineral density in breast cancer survivors taking aromatase inhibitors.”

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 the early 2000s, 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 usually aren’t used to reduce recurrence risk in premenopausal women.

Hormonal therapy usually is prescribed for 5 to 10 years after surgery.

Still, many women -- from about 25% to 40% -- who are prescribed hormonal therapy to reduce recurrence risk after surgery either don’t start taking the medicine or stop taking it early, in many cases because of side effects.

Weight gain, joint pain and stiffness, and loss of bone density are all side effects of aromatase inhibitors.

If doctors could find a way to ease some of the side effects caused by aromatase inhibitors, it’s possible that more women would stick to their treatment plans and take the medicines for as long as they’re prescribed.

This study, called the Hormone and Physical Exercise (HOPE) study, included 121 postmenopausal women diagnosed with stage I-III, hormone-receptor-positive breast cancer who had been taking an aromatase inhibitor for at least 6 months. All the women weren’t exercising when they study started, though they were physically able to exercise.

On average, the women in the study were about 60 years old, overweight, inactive, and had been taking an aromatase inhibitor for about 1.5 years.

The researchers randomly assigned the women to one of two groups:

  • One group (61 women) participated in a year-long exercise program; these women did supervised strength training 2 times per week as well as 2.5 hours of aerobic exercise at moderate intensity, such as brisk walking.
  • The other group (60 women) got the usual care after being prescribed an aromatase inhibitor: a recommendation to exercise and eat healthy food, as well as monthly calls to ask the women if they were taking the aromatase inhibitor as prescribed.

Results reported in 2013 from this study found that women in the exercise program had 20% to 30% less joint pain than women who didn’t exercise.

In this analysis, the researchers looked at body composition, including body mass index (BMI), percentage body fat, lean body mass, and bone mineral density.

Body composition was measured:

  • just before the study started
  • 6 months after the study started
  • 1 year after the study started

Compared to women in the usual care group, women in the exercise group:

  • had more lean body mass
  • lost more body fat
  • had a bigger decrease in BMI

All these differences were statistically significant, which means they were likely because of the difference in exercise rather than just due to chance.

After a year, there were no differences in bone mineral density between the two groups.

"We noticed a drop in percent body fat and body mass index, as well as a significant increase in their lean body mass," said Gwendolyn Thomas, assistant professor of exercise science at Syracuse University and one of the study’s authors. "These changes have clinical benefits, but also suggest that exercise should be prescribed in conjunction with AIs, as part of a regular treatment regimen.

"There are so many barriers to exercise in everyday life," she continued. "We can tell our patients they need to exercise, but helping them meet their goals is something at which we [as exercise scientists] need to do a better job."

Helping breast cancer survivors meet their exercise goals is Thomas’s next project. She is recruiting participants for another study that aims to develop a fitness app for breast cancer survivors.

While the side effects of hormonal therapy can be troubling, they’re overshadowed by the reality that hormone-receptor-positive breast cancer can come back. Hormonal therapy after surgery reduces that risk. If you’ve been prescribed hormonal therapy after surgery, you must remember this.

There are steps you can take to get rid of any obstacles stopping you from doing all you can to lower your recurrence risk. If side effects are a major problem for you, talk to your doctor about ways to manage them. You also may be able to switch to a different hormonal therapy.

If you’re currently taking an aromatase inhibitor, try to make exercise part of your daily routine. Think of exercise as another important part of your overall treatment plan that helps you recover and stay healthy. If you’ve never exercised before, the first thing to do is to talk to your doctor and possibly a certified fitness trainer about a safe and sensible plan designed specifically for you and your needs and physical abilities. It's also a good idea to talk to your doctor about a healthy weight for your age, height, body type, and activity level.

You may want to start gradually, maybe walking for 15 minutes a day, and then slowly increasing the amount of time you spend exercising as well as the intensity level of each session. You may need months to work your way up to 150 minutes a week, but that's OK.

If you're not sure how to start exercising, you might want to visit a gym or make an appointment with a certified personal trainer to learn about different types of exercise. Some people prefer exercising in their homes using videotapes or DVDs. Others find great joy in gardening or building things, as opposed to organized exercise. Some people love being part of a team and playing soccer or baseball. Walking or jogging with a friend is a great way to socialize AND get the benefits of exercise. Dancing to great music is great exercise. With so many different ways to move, you're bound to find a way to exercise that suits your personality and schedule. If you can find one or a mix of exercises that you think are fun and not boring, you'll be much more likely to stick with it.

In the Breastcancer.org Exercise section you can learn about:

  • the benefits of exercise
  • types of exercise
  • when you can and can't exercise during treatment
  • how to exercise safely
  • tips on finding a trainer

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