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Exercise and Breast Cancer Protection: What, Why and How?

We all know exercise is fantastic for us physically and mentally. Exercise helps to maintain a healthy weight, strengthens bones and muscles, reduces the risk of cardiovascular disease, Type 2 diabetes and metabolic syndrome, improves the ability to do daily activities and improves mental health and mood. Maybe surprising to some, is that exercise also reduces the risk of certain cancers, including breast cancer initiation and recurrence.

Over a hundred studies have investigated the relationship between exercise and breast cancer. Both large epidemiologic studies, following thousands of women over time, and smaller studies, examining differences between women with and without breast cancer, have shown that increased physical activity decreases the risk of developing breast cancer.

Reductions in breast cancer risk have been seen across subgroups of women—including pre- and postmenopausal women, women with different tumor subtypes, and multiple races and ethnicities. A recent review of published studies estimated the overall decrease in breast cancer risk to be 22%, with the reduction varying from 20-40% depending on the subgroup of women.

Stay Abreast of the Latest Foundation News and UpdatesSo what if breast cancer has already happened? Exercise is equally if not more important. Numerous studies have shown that being physically active lowers the risk of breast cancer recurrence and mortality, decreases treatment-related symptoms and longer-term collateral damage, reduces comorbid conditions (cardiovascular disease, diabetes and metabolic syndrome) and increases quality of life.   

The evidence for both risk and survivorship is strong enough that you cannot read a women’s magazine or sit in a doctor’s office without seeing a picture of a woman wearing pink while running or doing yoga to promote exercising to decrease risk of breast cancer or promote health during and after breast cancer treatment.

So why are we having this conversation? Well, we don’t have a perfect prescription for exercise and even if we did, getting people to exercise is really difficult.

First let’s talk about an exercise prescription. The exercise advertisements probably do not state what kind of exercise or the dose of exercise (how much and how long) to lower risk—and that is because we still do not know the magic dose.  

We would never hand a patient a bottle of medication without instructions on dose. Instead, we study the biological mechanisms of the medication and how it works in the body to decrease or treat disease. A final dose is determined based on effectiveness and safety. Exercise is no different. Therefore, in order to determine the most effective exercise dose, the most recent research has focused on determining the biological mechanisms underlying the association between exercise and breast cancer risk reduction. 

We know that increased weight is associated with breast cancer. Therefore, decreasing weight through exercise is an obvious mechanism for decreasing risk. But what else could be lowering risk? In the current, and very exciting, era of translational research, we are now able to merge the worlds of wellness interventions with laboratory “bench” science to find out.

Scientists have exercised mice, yes mice running on treadmills is a thing, to show that exercise affects multiple biological pathways including immune function, hormones, inflammation and DNA repair, and may even inhibit tumor onset and progression. But WE are not mice…

So several researchers like myself have designed exercise interventions across the breast cancer spectrum looking at the ability of exercise to modify biological pathways known to be involved in breast cancer initiation and progression. We compare biospecimens before and after exercise.

A fun way we like to describe it on our team is that we are studying whether exercise can change how our DNA works and whether we can “train” our cells though exercise to behave most effectively and efficiently. Just like we train our muscles and bodies in the gym, we believe we can also train our cells.

Sure enough, human studies are corroborating what we have observed in mice. In human exercise intervention studies, beneficial biological changes have been observed in as little at 3-4 months of consistent exercise. The most notable changes have been seen in inflammation, immune function, DNA repair and hormonal pathways. Interestingly, these changes are even observed without significant weight loss.

The more we learn about the biological changes the more we will be able to tailor exercise recommendations based on which biological change we want to target for prevention. For example, to decrease risk of breast cancer we may need a specific type/dose of exercise that is different than the one we need to help during chemotherapy treatments and that is different than the one we need to decrease metabolic syndrome after treatment. In addition, it is entirely possible that for one person it may require training for a marathon to get biological change versus walking up and down a hallway for another person. Just as we are moving into personalized medicine, we may be moving into personalized health prescriptions as well.

Until then…just get up and move, and decrease your time sitting! And if you need numbers, the guidelines provided by the World Health Organization and the American Cancer Society are a great start—strive for 150 minutes per week of moderate to vigorous activity (>3 metabolic equivalents). What does that mean? Brisk walking. Yes, brisk walking!

That brings me back to the second point of discussion…what will women actually do? We know exercise is great for us, but very few of us actually do it! Even if we find the ultimate dose of exercise that will cure everything, it will be useless if no one will do it. We need exercise that is feasible for the average woman to maintain.

Therefore, several of us have taken a different approach to studying exercise. Our team’s goal is to determine the minimum dose of exercise necessary to elicit a protective biological response.

In other words, can we get similar biological results that have been observed in exercise laboratories with one-on-one high-intensity training—but using more moderate and community-based programs? Our data is preliminary, but so far it looks like a yes!

In both women who have no history of cancer or diabetes and in women who have been recently treated for breast cancer, we have seen increases in quality of life and biological changes with walking, and with community-based programs such as Curves, Zumba and Crossfit. We have even found that exercise over a few months can turn genes on and off. Among our women who have been treated for breast cancer, all forms of exercise seem to alleviate both treatment-related symptoms and collateral damage.

A recent review of exercise intervention trials in breast cancer survivors showed some very interesting results. Yes, exercise was still shown to be beneficial, however the strongest benefits came from the studies that combined nutrition and exercise, incorporated a social support component and/or cognitive-behavioral therapy.

Additionally, when the intervention is tailored to where a woman is in the breast cancer journey, adherence was higher and results were stronger. For instance, for women who are currently undergoing treatment having an exercise program in the clinic that can be easily accessible before or after chemotherapy/radiation treatments is feasible and helpful. However, for women finished with treatment, they may not want to exercise in the clinic; therefore community-based interventions may be most feasible and helpful.

At the Claremont Club in Claremont, CA we are examining the feasibility of a wellness program for cancer survivors—The Living Well After Cancer Program—and the ability of the program to affect health and wellbeing. The 13-week program for all cancer survivors, including those living with metastatic cancer, incorporates exercise, nutrition and social support. The program is ongoing and starts three times a year. Based on the preliminary data of our first 20 participants, we not only found that the program is feasible, but we have found that at 13-weeks, several measurements—including weight, glucose, cholesterol and lipids—were significantly lower. Additionally quality of life went up and treatment-related symptoms went down. Our next 20 participants finish their program in late May and we are currently in the process of growing the program and developing tailored programs including one specifically for women living with metastatic breast cancer.

Key Points:

  • Exercise is an inexpensive way with virtually no side effects to increase your physical and mental health!
  • We know it can decrease risk of breast cancer initiation, progression and recurrence and researchers are currently determining how in order to develop the most effective dose.
  • At the same time, we know it is hard to get people to exercise, therefore researchers are also tailoring programs to be feasible for the average woman to maintain.
  • We also know that exercise can really help lessen and even prevent treatment-related side effects and longer-term collateral damage in both early stage breast cancer and metastatic breast cancer.
  • Lastly…It’s never too early or too late to get up and move!

—Jessica Clague DeHart, PhD, MPH