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Health and medicine

Exercise a foe of breast cancer

Even walking reduces a patient's risk of death from the disease, a study says. But post-treatment exercise is easier to suggest than do.

By LISA GREENE
Published May 25, 2005

Most people who exercise for better health think of the obvious advantages: warding off heart disease, diabetes and weight gain.

But exercise has another, more surprising benefit as well: It can help breast cancer patients cheat death, says a study published in today's Journal of the American Medical Association.

Women don't have to be triathletes. Even walking for an hour a week reduces the risk of death from breast cancer by 20 percent for women already diagnosed with the disease, the study found.

"I hope women with breast cancer consider that exercise may improve their length and quality of life," said Dr. Michelle D. Holmes, assistant professor at Harvard Medical School and the study's lead author.

Exercise also helps prevent breast cancer, other studies have said. But this study found exercise helps women who already have the disease. The news could have a dramatic effect on their lives, since they are likely to exercise less after getting cancer.

Less than one-third of breast cancer survivors get as much exercise as the government recommends.

"The stress of treatment and a life-threatening illness can be very discouraging to women," Holmes said.

The study is especially important coming just after another study linking lower-fat diets to lower breast cancer recurrence, said Dr. Larry Norton, deputy physician-in-chief for breast cancer programs at Memorial Sloan-Kettering Cancer Center.

"There seems to be a connection between fat in your body, fat in the diet and recurrence of breast cancer," he said. "It's very exciting, because it's something we can do something about."

More exercise reduces the risk further. The greatest benefit is to women who exercise the equivalent of walking three to five hours per week. Those breast cancer patients reduced their risk of death by 50 percent. Women who exercised harder could spend less time working out for the same benefit.

The study results impressed Clearwater resident Roberta Mindykowski. She has battled breast cancer for nine years. Mindykowski, 60, had a mastectomy nine years ago. Three years ago, her cancer returned, and two years ago she had more surgery.

Exercise after cancer is easier recommended than done. After her latest surgery, Mindykowski said, her energy disappeared.

"It takes a long time to get your stamina back," she said.

It wasn't until a few months ago that Mindykowski resumed regular exercise. Now she's lifting weights, walking on a treadmill, and taking daily breaks to walk in her office parking garage with co-workers.

"Just doing a little bit of exercise makes you feel so well mentally and physically, it can't do anything but help you," she said.

The study looked at data from almost 3,000 patients in the ongoing Nurses' Health Study who were diagnosed with breast cancer between 1984 and 1998, following them until 2002.

Researchers analyzed how much exercise women reported getting after they were treated for breast cancer. They didn't include women with the worst prognosis, or women undergoing treatment, since both groups would be less likely to exercise.

Of the study participants, 86 percent survived at least 10 years after diagnosis.

Researchers aren't sure why women who exercised were more likely to survive. Exercise may help because it lowers the level of estrogen circulating in women's bodies.

The study found that exercise reduced the risk most for women with the most common kind of tumor, which is stimulated by estrogen. That gives more weight to the idea that the benefits come from affecting estrogen levels, Holmes said.

Other factors also may be at work, Norton said. In the recent diet study, lower-fat diets still affected tumors not stimulated by estrogen. That makes him wonder whether some chemical in fat cells affects breast cancer and that chemical is in turn affected by diet and exercise.

The study's findings are "fairly convincing," said Dr. Pamela Munster, breast cancer oncologist at H. Lee Moffitt Cancer Center & Research Institute and assistant professor at the University of South Florida.

Still, the study has limits. Because the women chose whether to exercise, rather than being assigned at random to exercise or not, it's possible that there was some other difference between the two groups, Munster said. Maybe women who exercise visit their doctors more often, or eat more vegetables.

Researchers tried to account for such factors, Holmes said, but "can't totally rule it out" that something else might have influenced the results.

Munster would like to see the results confirmed in a randomized trial. But in the meantime, the best bet is to hit the gym, she said.

"Even a woman with breast cancer is still at risk of dying from heart disease," she said.

Holmes agreed.

"There's not a lot to lose by exercising," she said.

Cindi Crisci, 45, of St. Petersburg worked out and watched her diet because her family has a history of heart disease.

Six years ago, Crisci was diagnosed with breast cancer. She walked after her surgeries, through her chemotherapy and her radiation treatments.

"It helped in the healing process," said Crisci, whose cancer prompted her to get a job with the American Cancer Society. "I firmly believe a positive attitude and staying healthy helped me. ... Exercise in general helps the mind, body and soul."

Why would exercise keep breast cancer from coming back, or spreading throughout the body? Researchers aren't sure. But studies have linked exercise to lower levels of estrogen in the body. And today's study found that women whose tumors are stimulated by estrogen got even more benefit from exercise. So they believe exercise may help prevent cancer because it lowers estrogen levels.

[Last modified May 25, 2005, 09:40:47]