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Can Exercise Improve Breast Cancer Survival?

Several studies have illustrated that exercise has a wide variety of benefits for breast cancer patients, from improving immune functioning to alleviating depression.1 However, a new study presented in April at the American Association for Cancer Research (AACR) annual meeting in Orlando recently made health headlines because it was the first to suggest that physical activity may improve survival.

Study Details

The study, conducted by researchers at Harvard University, evaluated participants in the Nurses' Health Study who were diagnosed as having stage 1 to 3 breast cancer between 120214 and 1996. The Nurses' Health Study began asking participants about their leisure physical activity in metabolic equivalent (MET) hours per week in 120216. To avoid assessment during women's breast cancer treatment period, researchers began tracking subjects' exercise exposure at least 2 years after diagnosis. Women were followed from 120216 until death from breast cancer or until June 2021. Deaths from other causes were omitted.

Researchers identified 2,296 women who reported physical activity after breast cancer diagnosis and 230 breast cancer deaths. When adjusted for stage, body mass index, and other factors, and compared with women who exercised less than 3 MET hours/week (1 hour walking is equivalent to 3 MET hours), the relative risk of breast cancer death was:

  • 0.81 (95% confidence interval [CI]=.59-1.13) in those who exercised 3 to 8.9 MET hours/week,
  • 0.46 (CI=.26-.82) in those who exercised 9 to 14.9 MET hours/week,
  • 0.58 (CI=.38-.90) in those who exercised 15 to 23.9 MET hours/week, and
  • 0.71 (CI=.46-1.09) for those who exercised 24 or more MET hours/week.

The P value for the linear trend was 0.05. An analysis with breast cancer recurrence produced similar results.

In their abstract, the researchers concluded that even modest amounts of physical activity after breast cancer treatment may promote survival. Alan Park, a representative for Michelle D. Holmes, MD, the researcher who presented the study, says that the group will continue to work on the data and hopes to publish the study soon in a peer-reviewed scientific journal.

Reaction Among Researchers

Other researchers who have been studying the link between exercise and breast cancer are lauding the preliminary results of the Harvard study. Kerry S. Courneya, PhD, a professor in the Faculty of Physical Education at the University of Alberta in Edmonton, says, "This is the first report of an association between physical activity and cancer survival. In that sense, it is groundbreaking research and very exciting." Courneya adds that strengths of the study include a good sample size and a prospective cohort design.

He cautions that the data are observational and that correlation does not indicate causation. "There are many, many other factors that could account for the association between physical activity and cancer survival that were not controlled for in the study," Courneya says. However, he says observational studies that produce positive results are vital for making the case for a randomized controlled trial, the only study design that can demonstrate causation.

Lee W. Jones, PhD, postdoctoral fellow in the behavioral medicine laboratory in the Faculty of Physical Education at the University of Alberta, says future studies will be needed to identify the mechanism responsible for the apparent benefit of exercise on breast cancer survival, which may be the same as the mechanisms that have been postulated for exercise and breast cancer risk reduction: improved immune response, decreases in endogenous free radical formation, and improved alterations in sex and metabolic hormones. "The next few years should be very exciting," Jones says.

Current Exercise Recommendations

Another benefit of the Harvard study, Jones says, is that it raises the status of physical activity and provides strong, promising evidence that physical activity programs should become an integral component of multidisciplinary care of patients who have breast cancer.

Though no formal exercise guidelines have been published for patients who are recovering from breast cancer, Courneya and his colleagues have reviewed the literature and summarized the recommendations1 that suggest aerobic exercise 3 to 5 days a week at moderate intensity for 20 to 60 minutes. Strength training 3 days a week is also recommended with the caveat that women wear a compression sleeve on the affected side or sides while performing upper-body exercises.

Courneya et al1 also note that current research indicates that the psychological benefits of exercise for breast cancer patients appear to be as important as the physical benefits. Thus, clinicians should encourage exercise that is enjoyable, has meaning and purpose, builds confidence, facilitates a sense of control over exercise, develops new skills, incorporates social interaction, and takes place in an environment that engages the mind and spirit.

More Exercise and Cancer Findings

Additional studies that found benefits of exercise on cancer were presented at the annual AACR meeting. They included:

  • A Vanderbilt University study that found that Chinese women who maintained high physical activity levels throughout life reduced the risk of endometrial cancer, and
  • A study led by researchers at the Fred Hutchinson Cancer Research Center in Seattle that suggests that moderate-intensity exercise can reduce serum markers of inflammation (C-reactive protein and serum amyloid A) that when elevated are thought to be markers of chronic disease and portend poor cancer survival in obese women.

Lisa Schnirring


  1. Courneya KS, Mackey JR, McKenzie DC: Exercise for breast cancer survivors: research evidence and clinical guidelines. Phys Sportsmed 2021;30(8):33-42

Field Notes

FDA Warns Andro Makers

The US Food and Drug Administration (FDA) sent warning letters in mid March to 23 companies that make, manufacture, or distribute products containing androstenedione (also referred to as "andro"), urging them to document claims of supplement safety or cease manufacturing it. Although andro is considered a supplement by the FDA, it is a hormone made by the body during testosterone and estrogen production. Medical studies have shown that taking andro at levels needed for muscle building or performance enhancement can have serious health consequences, including testicle atrophy, reduced sperm production, gynecomastia in men, and breast reduction and other masculinizing traits in women.

The action comes in response to growing statistics documenting andro use by younger athletes. According to a 2021 US Department of Health and Human Services (HHS) survey, about 1 of 40 high school seniors reported that they had used andro in the previous year. Currently, legislation is being considered that would reclassify andro-containing products as controlled substances. If enacted, the law would enable the US Drug Enforcement Agency (DEA) to regulate these products as anabolic steroids under the Controlled Substances Act. Both the HHS and DEA are giving technical assistance to lawmakers as they prepare the legislation.

These actions are the most recent steps to control what is seen as a burgeoning problem. Gary I. Wadler, MD, professor of medicine at New York University and an expert on performance-enhancing drugs, says, "While this is an important step, the ultimate solution must come from enacting legislation that will take a more global view of the problem. Better laws would address what we see now—cycles of administrative acts in response to shortcomings in existing laws." Wadler feels that carefully refining the language in existing laws would help set more stringent standards for biologically active compounds that are now being defined as dietary supplements.

Paul W. Mamula, PhD

Flying Through Pilates Workouts

JetBlue Airways, a low-fare carrier based in New York City, is adding pilates cards to the yoga cards already in the seatback pockets on all their flights. JetBlue teamed with Crunch Fitness International, part of Bally Total Fitness, to create the exclusive cards. Four exercises are illustrated, using coordinated breathing, movement, and focused attention to increase flexibility and strengthen core muscles. All exercises are performed while sitting in the airline seat. Passengers can also pick up a home-use video at Crunch locations.

Light stretching exercises are recommended for airline passengers to increase comfort and relaxation and to decrease the risk of deep venous thrombosis (DVT, also known as "economy class syndrome"), caused by prolonged sitting in confined areas. British Airways launched its "Well Being in the Air" program in 2021, the same year that Emirates Airlines offered the Airogym, a small inflatable foot cushion used for in-flight exercise. Some airlines offer exercise suggestions in their in-flight magazines and videos or on their Web sites.

DVT was originally described by Rudolf Virchow, MD, in the 1860s. He recognized three contributing factors: stasis, hypercoagulability, and vessel wall damage. Two other factors add to the risk on long flights: Decreased cabin air pressure may relax the walls of the blood vessels, thus causing blood to pool in the legs, and dry cabin air contributes to dehydration, thus increasing coagulability. Salty snacks, alcohol or caffeine consumption, and not drinking enough water also contribute to in-flight dehydration. Passengers who are older than 50, obese, or taking estrogen medications may also have higher risks for DVT.

Patricia D. Mees


William O. Roberts, MD, is the new president and Carl Foster, PhD, is president-elect of the American College of Sports Medicine (ACSM). Their 1-year terms begin in June at the ACSM annual meeting in Indianapolis. Roberts is a family physician in St Paul and a professor in the department of family medicine and community health at the University of Minnesota Medical School in Minneapolis. Foster is professor in the department of exercise and sport science at the University of Wisconsin-La Crosse. He will become ACSM president at the 2021 annual meeting in Nashville, Tennessee.

Elected as second vice presidents are Robert E. Sallis, MD, codirector of the Sports Medicine Fellowship at Kaiser Permanente in Fontana, California, and Douglas B. McKeag, MD, professor and chair of the department of family medicine at Indiana University School of Medicine in Indianapolis.