Breast cancer: Keeping abreast of how to lower your risk

Breast cancer strikes more women than any other cancer and kills more women than any cancer except lung cancer. And despite decades of research, there are no magic bullets. “The good news is that there is something you can do to lower your risk,” says Walter Willett of the Harvard School of Public Health.

It’s not clear if soy or vitamin D can lower your risk of breast cancer. It is clear that fruits and vegetables can’t (though they should protect your heart and waistline). In contrast, hundreds of studies show that avoiding weight gain, exercising, and limiting alcohol can lower breast cancer risk (though there’s no guarantee).

Here are four steps that will most likely lower your risk.

Watch your weight

“Probably the single most important thing women can do to reduce their risk of breast cancer is to avoid weight gain in adult life,” says Willett. That may surprise many women, since researchers were still saying that weight had no impact on breast cancer as recently as the early 1990s. Two factors obscured the link.

“Part of the problem is that obesity is protective at young ages,” explains Regina Ziegler of the US National Cancer Institute. Premenopausal women who are heavy have a lower risk of breast cancer. “What’s more important, extra pounds only matter in postmenopausal women who are not taking hormones,” adds Ziegler.

In women who take no hormones, “being overweight increases risk two- to three-fold,” says Rachel Ballard-Barbash, also of the US National Cancer Institute. “So, you see it as a strong risk factor.” And not just for women who are obese. “We see the increase in risk at a BMI of about 27, so it’s before obesity, which is a BMI of 30,” says Ballard-Barbash. (A woman who is 5’5” has a BMI — or body mass index — of 27 if she weighs 165 pounds and a BMI of 30 if she weighs 180.)

“The increased risk isn’t of much significance with a 10- to 15-pound weight gain, like it is with diabetes,” she adds. “But gaining 20 to 30 pounds after age 18 certainly increases your risk.”

How do extra pounds harm your breasts? “There are now about six to seven mechanisms that scientists are exploring, says Ballard-Barbash. The most popular theory involves estrogen. Estrogen — which travels through the bloodstream largely as estradiol — promotes breast cancer. In the postmenopausal period, the ovaries are no longer producing estrogen. That means the main source of estrogen is fat cells. So the more fat cells you have, the higher your levels of estrogen. But being overweight has little impact on women who take hormones after menopause because the estrogen in the pill swamps the estrogen that their fat cells produce. So for those women taking hormones, the little extra addition of estrogen from fat cells has little effect. “You can’t see it on top of the increased risk from the hormones,” says Ballard-Barbash.

Estrogen may also explain why heavy young women have a lower risk of breast cancer. For reasons that are unclear, they have lower estrogen levels than normal-weight young women. But the bottom line is this: “Whether you start out fat or thin or medium at age 20, putting on weight after that increases your risk of postmenopausal breast cancer,” says Ziegler.

Avoid Taking Hormones

The news came as a shock. In July 2002, the US National Institutes of Health (NIH) announced that it was halting the Women’s Health Initiative Trial because women taking hormones after menopause had more breast cancer than those taking placebo. “A 26-percent increase in breast cancer risk is too high a price to pay, even if there were a few health benefits,” explained Claude L’Enfant, then director of the US National Heart, Lung and Blood Institute.

Hormone sales plummeted by 38 percent by the end of 2002 and by 2004, breast cancer had dropped by roughly 11 percent — the first time they had fallen significantly since 1945. Tumors that are fueled by estrogen, which accounts for 70 percent of all breast cancers, fell by 15 percent. “The connection is astounding,” reported The New York Times.

“Prolonged hormone replacement therapy (HRT) strongly elevates postmenopausal breast cancer risk,” says Willett. “We found in the Nurses Health Study several years ago that the combination of HRT and weight gain during adult life explains about half of breast cancer mortality in the US.”

One bright spot: The increased risk from taking hormones drops within two or three years after women go off the pills.

Get Moving

Active women have a lower risk of cancer. “In probably 50 or more observational studies, the findings are reasonably consistent in multiple populations in multiple countries,” says Ballard-Barbash.

For example, an American Cancer Society study tracked more than 72,000 postmenopausal women who answered a questionnaire about leisure activities like walking, running, swimming, tennis, bicycling, aerobics, and dancing. After five years, the most active women had a 29-percent lower risk of breast cancer than those who exercised the least.

That exercise protects the breast “seems to be true for premenopausal and postmenopausal breast cancer,” adds Ballard-Barbash. It’s true for physical activity late in life, and there’s some evidence to suggest that being physically active throughout your life is even more protective.” How might exercise protect the breast? Since it reduces body weight and body fat, decreases in estrogen may be a large way in which it is operating,” explains Ballard-Barbash.

There’s also evidence that staying active may help women who have been diagnosed with breast cancer. “Eight studies have suggested that women who are physically active after a diagnosis of breast cancer are less likely, two years after their diagnosis, to have recurrent breast cancer or to die of breast cancer in a defined follow-up period,” says Ballard-Barbash. In one study, those who reported doing the equivalent of two to three hours of brisk walking a week were 70 percent less likely to die over the next six years than those who were inactive. “Most studies see a benefit at 30 minutes of walking a day, so it’s not a lot of exercise,” she adds. “A few women report dancing or jogging, but the primary activity is walking.”

Minimize Alcohol

“One of the best proven ways to lower your risk of breast cancer is to keep alcohol consumption low,” says Willett. “And low is pretty low. Even at one drink a day, we find a modest but significant increase in breast cancer risk.”

A recent British study added one more nail in the coffin. In the Million Women Study, which tracked more than 1,280,000 women for seven years, each daily alcoholic drink raised the risk of postmenopausal breast cancer by 12 percent.

A daily alcoholic beverage also raised the risk of cancers of the mouth, throat, esophagus, voice box, rectum, and liver. The total damage for each daily drink: 15 excess cancers in every 1,000 women. “From a standpoint of cancer risk, the message of this report could not be clearer,” wrote Michael Lauer and Paul Sorlie of the US National Heart, Lung and Blood Institute in an editorial accompanying the study. “There is no level of alcohol consumption that can be considered safe.”

And that’s critical even if alcohol helps lower the risk of heart disease. “Although it is true that cardiovascular disease is the leading cause of death among women overall, this primarily applies to women older than 75 years. Among women, the major cause of death by far during the middle years is cancer,” note Lauer and Sorlie. And for middle-aged women, they add, “the only reasonable recommendation we can make is that there is no clear evidence that alcohol has medical benefits.”

The big picture for avoiding alcohol also applies to keeping weight off and exercising more. The benefits go far beyond breast cancer. “Being overweight increases the risk for cancers of the endometrium, colon, kidney, liver, thyroid, pancreas, esophagus, and gall bladder,” says Ballard-Barbash. The Million Women Study also found a higher risk of leukemia, multiple myeloma, non-Hodgkin’s lymphoma, and ovarian cancer among overweight women.

And shedding — or not acquiring — extra pounds can cut the risk of diabetes, heart attack, and stroke. Likewise, exercise lowers the risk of these illnesses, along with breast, colorectal, and other cancers. “So many women are worried about breast cancer that this concern may motivate them to exercise and stay trim, from additional fear of other diseases,” says Ziegler.

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 For good information about breast cancer, consult the following: American Cancer Society (www.cancer.org), Breastcancer.org (www.Breastcancer.org), and Dr. Susa Love Research Foundation (www.dslrf.org and www.armyofwomen.org). And don’t miss next week’s column on the latest advances in breast cancer management.