Exercise: A New Breast Cancer ‘Drug’?

The last thing Liz O’Riordan wanted to do after being diagnosed with stage III breast cancer was exercise. She did it anyway.

“I ran 5Ks with a bald head. I cycled to chemo, swam, and did a pool-based sprint-distance triathlon halfway through treatment — very slowly,” says O’Riordan, who was 40 and a breast cancer surgeon at the time of her first diagnosis in 2015. “I had a sense of freedom and control . It was the most important half-hour of the day.”

O’Riordan, who is based near Bury St Edmunds, UK, is in remission after her breast cancer came back in 2018. After her first diagnosis, she co-authored The Complete Guide to Breast Cancer: How to Feel Empowered and Take Control.

When it comes to exercise and breast cancer, she suggests you aim for time, not results. Her stamina dropped as chemo progressed, so she set a goal of 30 minutes each day. “It didn’t matter how far I went,” she says.

Researchers are discovering the numerous benefits of exercise after a breast cancer diagnosis.

“In the near future, we will think about exercise as we would medications,” says Neil Iyengar, MD, an associate attending physician in the breast medicine service at Memorial Sloan Kettering Cancer Center in New York City.

Living Longer

A federal study in 2021 found that women who exercised at least 2½ hours a week either before or after a diagnosis were less likely to have their cancer come back (what doctors call “recurrence”) and were less likely to die, compared with those who exercised less.

Several other studies have reported similar, positive results. But it’s unclear if exercise alone is responsible for the benefits, says Jennifer Ligibel, MD, a Susan G. Komen scholar and associate professor of medicine at Harvard Medical School.

Tolerating Treatment

Researchers are more certain that exercise can lessen side effects from breast cancer treatment, says Ligibel. It can ease your fatigue, anxiety, and joint pain. Physical activity may even make you more able to tolerate greater doses of treatment, says Erika Rees-Punia, PhD, a principal scientist at the American Cancer Society.

Physical activity improves quality of life in other ways, as well. “It dampens depression and makes it easier to manage ‘activities of daily living’ like lifting groceries or picking up a child,” says Rees-Punia, who is based in the Chicago area.

Continued exercise has continuing effects.

“Studies with cancer survivors show they develop problems of aging at a younger age. Physical activity can counter or slow this trend by protecting bones and preventing frailty,” says Karen Basen-Engquist, PhD, director of the Center for Energy Balance in Cancer Prevention and Survivorship at the University of Texas MD Anderson Cancer Center in Houston.

Why Exercise Helps

Researchers are still teasing out exactly how exercise provides these benefits. Theories include that it reduces levels of the hormones insulin and estrogen, both of which can contribute to cancer cell growth, says Basen-Engquist. Exercise can also aid weight loss, which can also lower the odds of cancer recurrence and death.

A more recent discovery is that exercise enhances the immune system, says Iyengar. A fortified immune system, of course, is better equipped to fight cancer.

What’s the Right Exercise ‘Dose’ for Breast Cancer?

This depends on the type of exercise and individual characteristics of the person, says Iyengar.

At a minimum, experts recommend meeting federal guidelines of 2½ hours of moderate-intensity cardiovascular activity (fast walking, biking on a flat surface) each week, along with muscle strengthening exercises at least 2 days a week. These are also the recommendations from the American Cancer Society and the American College of Sports Medicine.

“We used to recommend that women rest after breast cancer,” says Ligibel. “That was the worst thing to do. The more active you are through treatment, the easier it is to recover.”