Exercise and breast cancer survival: Making a connection - Cancer HealthLINK

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June 17, 2003

News this month
Exercise and breast cancer survival: Making a connection

Breast cancer patients tend to be less physically active following their diagnosis, a trend that could affect their overall health. This finding, from a new study published this April in the journal Cancer, is important since reduced physical activity can lead to an increase in body weight. Past studies have shown a connection between obesity and breast cancer recurrence and reduced survival.

Past studies have shown a connection between obesity and breast cancer recurrence.

Multicenter study
The paper’s lead author, Melinda Irwin, PhD, MPH., at Yale School of Medicine, conducted the research while a postdoctoral fellow at the Fred Hutchinson Cancer Research Center in Seattle. The study also involved researchers from the National Cancer Institute, the University of New Mexico and the University of Southern California.

Women in the study were participants in the NCI Health, Eating, Activity and Lifestyle (HEAL) study. The HEAL study has followed 1,065 women with early stage breast cancer since 1996. The goal is to establish whether weight, physical activity, diet, hormone receptors and other exposure have an effect on prognosis.

For this study, patients were recruited in New Mexico, California and Washington through the Surveillance, Epidemiology and End Results (SEER) registries. Patients in the study had early stage breast cancer from the selected geographic areas and were able to be monitored for 12 months after diagnosis. In the end, results from 812 women ranging in age from 45 to 75 years old were analyzed. About 61 percent were post-menopausal.

Assessing physical activity
During follow-up visits at four to 12 months post-diagnosis, women were asked how their physical activity levels compared to the year before diagnosis. They reported the type of activity they engaged in, the intensity level, and how long they performed the activity. Also studied was any association between physical activity and:

severity of their disease
type of treatment
age
body mass index

Women diagnosed with breast cancer…engaged in any sort of physical activity on average two hours less per week than before their diagnosis.

Intense treatment leads to decline
In this study, women diagnosed with breast cancer exercised or engaged in any sort of physical activity on average two hours less per week than before their diagnosis—an 11 percent decline. The most significant decreases in physical activity were observed among women who were already obese at diagnosis and those who received intensive treatment for their cancer.

Women treated with surgery, radiation and chemotherapy reported a 50 percent drop in physical activity
Women treated with surgery alone had a 24 percent decline, compared to a 23 percent drop among women treated with radiation only.
Physical activity among obese women declined the most—41 percent after diagnosis— compared to a 36 percent decline among overweight women and a 24 percent drop among lean women.

Connection between weight and breast cancer
Researchers have known for years that breast cancer patients at diagnosis who weigh more and have more body fat than lean women are at greater risk of recurrence and reduced survival. Exactly why this is so is not known. Scientists suspect that fat cells produce estrogens after a woman goes through menopause, which in turn stimulates breast cancer cells.

It is hoped that reducing overall weight or avoiding the weight gain after diagnosis could reduce recurrence and improve survival.

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Physical activity and breast cancer

It’s long been known that treating breast cancer early greatly improves chances of survival. But beyond early diagnosis, what other factors—such as weight, physical activity, diet, and hormone receptors—have an effect on a woman’s prognosis? These are some of the areas we are investigating through the HEAL study, which began in 1996.

“Many women gain weight during the first year after being diagnosed with breast cancer”

Studies have shown that many women gain weight during the first year after being diagnosed with breast cancer. This weight gain can have an adverse impact on cancer recurrence and survival. Many factors have been linked to causing the weight gain, including:

Receiving chemotherapy
Not taking tamoxifen
Decreased physical activity
Increasing caloric intake

Until now, few of these areas had been scientifically studied. Before our study, for example, there was little research that described the physical activity levels of women being treated for breast cancer. If we knew why women were gaining weight, perhaps there would be a better chance of taking action to reduce weight gain.

Results of study
In the study we looked at whether ethnicity, marital status, education, study site, tamoxifen use and family history played a role in decreased physical activity levels after diagnosis and they did not. Neither did depression, fatigue or nausea—common side effects of some forms of cancer treatment. Rather, the strongest predictor for decreased activity was body mass index and pre-diagnosis levels of physical activity (which are linked to BMI).

One disadvantage of our study was that we relied on women to recall the amount of time they spent in physical activity the year before their diagnosis. Ideally, a researcher would like to be able to measure in real time a person’s activity level to then see if it changed after the diagnosis. But that is not always possible for obvious reasons.

Inactivity is the wrong approach
When a woman is diagnosed with breast cancer, it can be an overwhelming time. A lot of women and health care professionals tend to shy away from encouraging exercise at this time. But that is the wrong approach—for many reasons.

“Exercise during breast cancer treatment can actually reduce—not increase—fatigue and nausea”

For example, for women undergoing aggressive therapy, small preliminary studies have shown that exercise during breast cancer treatment can actually reduce—not increase—fatigue and nausea. Without exercise, cancer patients can experience muscle wasting. Their metabolism declines and it makes them feel weaker. If you feel weaker, you do less, and it’s a circuitous problem.

Instead, we should be routinely directing cancer patients to exercise during their treatment. Treatment programs for cancer patients now are where cardiac rehabilitation was back in the 1980s. Before then, it was thought that exercise would be dangerous for heart disease patients. We now know the opposite is true. It would make sense to incorporate exercise into an overall cancer treatment program that would focus on increasing activity, smoking cessation and making healthy changes in diet to include more fruits and vegetables, fiber and low-fat foods.

Future research
We were looking at the connection between physical activity and weight gain after breast cancer diagnosis. Other studies are now looking at physical activity and its effect on hormone activity. We anticipate that in the future there will be several more studies investigating the relationships between physical activity, weight and cancer in the future.

Melinda Irwin, PhD, MPH, is an assistant professor in the department of epidemiology and public health at Yale School of Medicine.

Yale-New Haven was recognized this year by U.S. News & World Report for its cancer services.