Does Exercise Prevent Breast Cancer Recurrence?

In the September 2024 issue of the Natural Medicine Journal, I reviewed a new study that clarifies the relationship between exercise and breast cancer recurrence, specifically distant recurrence to areas outside the breast.  This was a large study conducted in France with over 10,000 participants, so it gives us more good data that helps deepen our understanding about how exercise impacts breast cancer survivors, how much is optimal, and who gets the most benefit.  While the findings confirm that exercise does help to prevent recurrence, I found the data to be somewhat surprising for a couple of reasons, which I will explain below.   Regardless of the findings in this study, moderate, regular exercise is so useful for breast cancer survivors.  

Some survivors will get even more benefit from exercise!

The findings in this study were somewhat surprising, in that they found more benefit for certain groups of survivors.   Particularly for women who had hormone receptor negative tumor subtypes, they found a 5-6% decrease in distant recurrence for women who exercised moderately at the time of diagnosis.  There was also a reduced risk of recurrence for all premenopausal women (aka: any woman who had not gone through menopause at the time of diagnosis).  Less benefit was found for women who had hormone receptor positive tumors and women who had gone through menopause before their diagnosis.  However, this does not diminish the value of exercise before, during, and after breast cancer treatment!

Exercise improves how effective your treatment is and how fast you recover.

The first great reason to exercise is is decreased mortality rates from breast cancer and all-cause mortality, as well as increased survival time for women diagnosed with stage 4 breast cancer. In addition to improved survival, exercise helps the treatment itself be more effective. Additionally, moderate exercise can significantly improve your quality of life as you go through and recover from treatment. Post-surgical exercises are crucial to retain mobility, promote healing, and prevent lymphedema, as well as reduce post surgical pain. (check out my course on Recovery From Lumpectomy and Mastectomy if you want to learn specific exercises) Not only is exercise useful for improving quality of life and mental health during chemotherapy, but women going through chemotherapy for breast cancer who were assigned to a home-based nutrition and exercise program were also more likely to have a pathologically complete response (aka–the chemo will get rid of all of the cancer) to their treatment regimen.  

Exercise is critical for mental health and quality of life.

Possibly the most impactful result of exercise in breast cancer survivors is improvement and maintenance of physical fitness and quality of life.  There are many studies that show exercise improves mood, decreases anxiety, and improves mobility before and after treatment. Regular exercise has been also been shown to reduce cancer-related fatigue and depression and improve sleep. 

There are so many other health benefits of exercise in breast cancer

The benefits of exercise of course extend beyond cancer specifically, to improving the overall health of breast cancer survivors.  It improves metabolic syndrome and cardiovascular health markers, which can be significant concerns for all postmenopausal women, but particularly for breast cancer survivors. Survivors who exercise moderately show increased lean muscle mass,  decreased adipose tissue, and decreased insulin and leptin.   Exercise can also decrease breast-cancer treatment related bone loss in premenopausal women. 

How much exercise is optimal for survivors?

So what is the ideal amount of exercise for women diagnosed with breast cancer? This study is one example of several that show that there is benefit up to a certain amount of exercise each week, with little benefit beyond the upper limit of that window. Before I get into the specifics, let me first explain how exercise is measured in clinical studies.  In these studies, they use a metric called “Metabolic Equivalent of Task” (or MET), which uses a scale of 1-12 for how intense your activity is.  1 would be no activity, like lying in bed, and 12 would be your fastest sprint.  A few examples of this would be a moderate walk would be 3.3, gardening would be a 4, a fast walk 5, playing tennis 8, and running 6mph 9.8. For some great information on this, you can check out https://www.whyiexercise.com/metabolic-equivalent.html.  This intensity score is then multiplied by the number of hours you perform this exercise each week (MET-h/week).

In this study, the amount of exercise necessary to show a significant decrease in distant recurrence starts at 5 MET-h/week and extends to 25 MET-h/week, with no additional benefit beyond this amount. If you aren’t used to exercise or have trouble with movement, this is good news.  5 MET-h/week is equivalent to walking 2mph, 15 minutes per day, 5 days per week; an amount achievable by almost any mobile person.  If you were active before diagnosis or if you are very motivated to do everything you can to prevent recurrence, you may find that adding intensity or duration to your workouts may be unnecessary.  25 MET-h/week is equivalent to  walking 4mph 60 minutes per day, 5 days per week, or running 6mph for 30 minutes per day, 5 days per week.

Exercise decreases overall mortality for breast cancer survivors

The World Health Organization states there is a decrease in all-cause mortality for breast cancer survivors at up to 10-15 MET/h-week, or 150 minutes of moderate to vigorous exercise each week.  A large meta analysis found a similar optimal benefit window for all-cause as well as breast cancer specific mortality, with greater benefit for those who exercise post-diagnosis rather than pre-diagnosis.  Also, a cohort of nearly 80000 breast cancer survivors showed decreased all-cause mortality for those who ran or walked at least 7.5 METh/week.

So the bottom line is–it’s a great idea to  exercise regularly before, during, after breast cancer treatment.  It’s critical for mental health, improves overall health, and decreases all-cause and cancer-specific mortality rates in women with breast cancer..  Exercise has the particular added benefit of decreasing distant recurrence rates in premenopausal women with hormone receptor negative tumors.  It’s important to remember though that more isn’t always better, and benefit can be derived from even small amounts of exercise.  If you were not active at the time of diagnosis, even adding a short, slow walk each day will make a significant difference.  If you are already active, you do not need to worry about “am I doing enough?”  Add the exercise that makes you feel good and more balanced, but rest assured that you are already doing enough.

Want to know more about Dr Kaycie’s support for breast cancer survivors? Check out Thriving Survivors

Here is Dr Kaycie’s article in the Natural Medicine Journal