Exercise + Breast Cancer: What You Need to Know Now!

Sylvie Normandeau was diagnosed with stage 3 aggressive breast cancer in April 2011. She had a double mastectomy, chemotherapy, radiation and took Tamoxifen for five years.

She was a personal trainer and freelance nutritionist who worked out three to five times a week and followed a healthy diet.

“I was already doing all the right things, and breast cancer still appeared,” she says.

Like many cancer patients undergoing treatment, the now 37-year-old found working out during treatment difficult. She took “a huge step back” and turned to more low-impact activities like yoga and meditation so she wouldn’t push her body too hard.

She even wondered if her body was meant to get cancer no matter how she treated it, so she gave up her green smoothies and other healthy habits. But they returned.

“I came back to giving my body a fighting chance, and I know these things are shown to improve your body functioning better overall,” she says.

As it turns out, Normandeau is right to believe that continuing to exercise after her breast cancer diagnosis gives her “a fighting chance,” as she puts it. A few weeks ago, the issue of breast cancer and exercise made headlines again, when a doctor and her research assistant at Toronto’s Sunnybrook Health Sciences Centre released a review of the most up-to-date research on the relationship between lifestyle factors, such as exercise, and the risk of breast cancer recurrence and mortality.

The problem was, conflicting headlines may have left readers wondering what to believe.

CBC News suggested that, “Exercise, keeping weight down help prevent breast cancer recurrence, review finds.” But the Globe and Mail said: “Analysis suggests lifestyle changes may not fend off breast cancer.”

The same analysis obviously didn’t offer two different conclusions, so we asked some experts, and the doctor herself, what the findings really mean.

The review

Dr. Ellen Warner and her research assistant, Julia Hamer, gathered together dozens of research papers, analyses and reviews that looked at how breast cancer recurrence or mortality are affected by lifestyle factors such as weight gain, exercise, diet (including soy and fats), smoking, alcohol and certain vitamins.

They found that, of all of the lifestyle factors, exercise had the “most robust effect” on breast cancer recurrence and mortality. In fact, starting an exercise regimen (or maintaining one) from the time of diagnosis right through treatment and afterward – a regimen is defined as 30 minutes of moderate to vigorous physical activity five times a week – increased chance of survival by 40 per cent.

“I was more surprised by the magnitude of the benefit because the benefit of the exercise is the same amount that we see with conventional treatment,” Warner said in an interview. That’s not to say that doctors should start advising women to replace conventional treatments, such as radiation and chemotherapy, with physical activity, she warned.

“We cannot say, ‘chemo reduces recurrence by 20 per cent, but with exercise we reduce it by 40 per cent so we’re not going to give you chemo,’” she said.

Exercise should still be only a part of an overall treatment plan. As Warner points out, exercise is also proven to lessen the side effects of treatment, including aches and pains, fatigue, anxiety and depression.

Normandeau herself isn’t surprised by the study’s findings. She believes exercise is “really vital” for overall health.

“Whether it’s for prevention of breast cancer or any other illness,” she said. “But I think prevention of recurrence is not a one-prong thing, it’s a lot of factors.”

What is it doing?

There is much still to learn about how, exactly, exercise is helping to reduce the risk of cancer recurrence and mortality. But research indicates that it affects several physiological pathways.

Exercise appears to impact how the body metabolizes sugars, Warner points out, and some studies have found a link between a diabetic or pre-diabetic state and cancer risk and recurrence.

Also, exercise regulates hormone levels, which could be beneficial when treating hormone-related tumours.
Physical activity also appears to reduce inflammation, which may explain why it reduces the aches and pains experienced by patients during treatment.

And of course, it can help with weight loss. According to Warner’s review, gaining more than 10 per cent of one’s initial body weight after diagnosis is linked to an increased risk of recurrence and death.

How much is best?

But questions do remain about how much, and at what frequency, is best. The 30 minutes, five times a week recommendation lines up now with not only what the Canadian Cancer Society and the American Cancer Society recommend, but what Health Canada advises everyone should set as their physical fitness goal just to maintain overall health.

What about specific “dosages” of physical activity being tailored to each patient to maximize the benefits? Research is headed in that direction to find if, and how, we can get to more personalized exercise “prescriptions.”

Dr. Christine Friedenreich, a world leader in research on the connections between physical activity and cancer, has found significant reductions in the risk of not only breast, but also prostate and endometrial cancers, with regular exercise.

Friedenreich, scientific leader for cancer epidemiology and prevention research at Alberta Health Services and adjunct professor and division head for preventive oncology at the Cumming School of Medicine, says the current guidelines, which add up to 150 minutes of moderate activity per week, or 75 minutes of vigorous activity, “are fine.”

“But there are lots of questions about exactly the dose, the timing, the duration, the frequency, the type of activity that we’re still investigating and that we don’t have the definitive evidence yet,” Friedenreich says. “

“But while that evidence is accumulating,” she adds, the American and Canadian Cancer Societies have at least deemed exercise safe for patients.

Dr. Daniel Santa Mina certainly agrees with that. He’s a scientist in the cancer rehabilitation and survivorship program at Princess Margaret Hospital and an assistant professor at the University of Toronto’s faculty of kinesiology and physical education.

He runs a wellness and exercise program at PMH that conducts comprehensive fitness assessments of referred patients before assigning them to a rehabilitation centre, an off-site program such as Wellspring or Gilda’s Club, or an eight-week group fitness program at the hospital that includes education on everything from fatigue to diet to emotional health.

As often as possible, his team aims to get patients physically active close to their time of diagnosis, before they begin treatment, so they know how their exercises are supposed to feel when their body is healthy.  That education can also help prevent them from over-exerting themselves.

“I think that for the most part, people are aware that exercise is good for them, but after a cancer diagnosis, and especially after some of these complex treatments, knowing what they should and should not do is very challenging, it’s very stressful. So making decisions sometimes becomes more difficult than it’s worth, and rather than trying something or finding somewhere to go, they remain inactive,” Santa Mina said.

“So we try to provide them with the education to become active even after the program ends.”  

While his team tailors programs to each patient, he said the question of dosage is really key for scientists to focus on to “optimize the effect” of exercise.

Although 150 minutes of physical activity each week may be the current target, “it’s not the only target,” he says. Patients who are not physically active at the time of diagnosis have to start somewhere.

“If you are doing nothing, then your target is whatever is a little bit more than nothing,” he says. “Then you incrementally gain benefit as you incrementally increase your physical activity.”

 Vigorous activity = better?

It’s been Friedenreich’s research that has led the way to reaching many of the conclusions that currently guide physicians’ recommendations, and for setting the path to study how it is that exercise actually impacts the body to reduce cancer risk.

The Alberta Physical Activity and Breast Cancer Prevention (ALPHA) Trial and the follow-up BETA trial looked at the impact of 45 minutes of moderate-to-vigorous exercise five days a week on what Friedenreich calls the “intermediate factors” for breast cancer: body fat, insulin resistance, sex hormone levels and inflammation.

In ALPHA, the researchers found that the more women exercised, the greater the impact on these markers. In BETA, some women were randomized to do 150 minutes of exercise per week, while others were given 300 minutes.

While both groups saw impacts in all areas, the group that did twice as much exercise didn’t enjoy a significantly greater benefit. However, women who spent more time in their target heart rate zone – meaning they did more vigorous exercise – did.

“So it does seem like if you’re able to do more vigorous intensity activity that there might be even more benefit to you,” she says.  

These studies looked specifically at post-menopausal women. And while the findings are “somewhat applicable” for pre-menopausal women, she said, there is research underway that will help drill down on how exercise might uniquely affect younger patients.

Friedenreich has a cohort study underway, the AMBER study, where 1,500 breast cancer patients are being recruited at time of diagnosis. Unlike observational studies, which require participants to fill out surveys or self-report their physical activity levels and other factors, a cohort study includes specific measurements of exercise, diet, other lifestyle factors, as well as blood tests and other physical assessments. The participants will also wear accelerometers to measure physical fitness levels, and they will be followed up with at one, three and five years.

The research team will also collect biological samples to study the participants’ tumours and gather information on their treatment to determine if there are any tumour subtypes that may be more responsive to physical activity, she said.

For Santa Mina, Warner’s review and other research are all part of a “snowball” that’s been building since as far back as the 1980s, when findings about the benefits of exercise for breast cancer patients began to emerge.
“The point being is physical activity is good for the healthy person without cancer in a very similar way that it is for people with cancer,” he says.

But getting people to do it “is the tricky part,” and patients will exercise for different reasons, enjoy different activities and tolerate didn’t levels of discomfort, he said.

Ultimately: “The dose that works, is the dose that someone is willing to commit to.”


Andrea Janus is a freelance writer and editor in Toronto whose work can be found at CBC.ca/Toronto and the Toronto Star, among other outlets. She spent seven years as a health and politics reporter at CTVNews.ca, and has always had a keen interest in breast-cancer research and related issues due to a strong family history of the disease. You can reach her at andrea@andreajanus.com.

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