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Do antiperspirants cause breast cancer? Are mammograms dangerous? MSNBC asks the experts to weigh in on some common breast cancer myths.

Few diseases are as feared by American women as breast cancer. Though researchers have learned a lot about it in recent years, many unknowns still remain. Out of these fears and uncertainties come myths, increasingly in the form of Internet rumors.

Despite public education efforts, many women fall into the trap of believing these falsehoods, which can keep them from following proper precautions, putting their lives at risk. Some common myths:

If breast cancer doesn’t run in your family, you don’t have anything to worry about.
Family history is a significant risk factor for breast cancer — having a first-degree relative, such as a mother, sister or daughter, with breast cancer can double a woman’s risk of developing the disease. However, women without a family history of the disease are far from free and clear.

“Only about 10 percent to 20 percent of women diagnosed with breast cancer actually have a family history of this disease, so if we were only to screen women with a family history of breast cancer, we would fail to diagnose the overwhelming majority of cases that occur in this country each year,” said Robert Smith, an epidemiologist and director of cancer screening for the American Cancer Society.

About one in eight women who lives to be 80 in the United States will develop breast cancer during her lifetime, according to National Cancer Institute estimates.

“The average woman has a high enough risk without having a family history to warrant being vigilant and not assuming that things are OK,” said Dr. John Glaspy, an oncologist at UCLA’s Jonsson Cancer Center.

Recent studies have shown that most cases of hereditary breast cancer stem from mutations of the BRCA1 and BRCA2 genes. Women with relatives who have had the disease can be screened for these mutations. But testing positive for a mutation doesn’t predict with certainty that a woman will develop the disease — about half of women who carry the mutations don’t develop breast cancer.

If you lead a healthy lifestyle (exercising, eating a low-fat diet and avoiding alcohol), you can prevent breast cancer.
While a healthy lifestyle may improve your odds of avoiding a variety of ailments, it is not a guarantee of breast health.

“We hope some day to know how breast cancer can be prevented but we are a long way away from prescribing a particular lifestyle that can significantly or even certainly reduce a woman’s risk,” Smith said.

There is some evidence linking alcohol consumption, obesity and high-fat diets to increased breast cancer risk, but Smith says much more research is needed to confirm these findings.

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In about two-thirds of breast cancer cases, there are no identifiable risk factors, said Dr. Mary Disis, an associate professor of oncology at the University of Washington School of Medicine in Seattle.

“Certainly, not smoking and eating a high-fiber, low-fat diet will impact your health in lots of different ways, decreasing your risk of coronary artery disease and things along those lines … but how much those reduce the risk of developing breast cancer we don’t know at this time,” Disis said.

Doctors emphasize that breast cancer is caused by a combination of factors, including genetics and lifestyle.

“We’re learning there isn’t just one cause of breast cancer, and the same factors will influence women in different ways. We know that two women can have exactly the same risk profile and one will develop breast cancer and the other will not,” Smith said.

Disis says that since there’s no way to prevent breast cancer, women’s best bet is to try to catch it early before it spreads with routine mammograms as well as self-exams and clinical examinations by your doctor.

While lifestyle changes may not give women the peace of mind they are looking for, there are more drastic risk-reducing steps to prevent the disease, such as taking the hormone-blocking drug tamoxifen, available to women in very high-risk groups (such as those with the BRCA1 or BRCA2 mutations, or those who have already had a cancerous tumor in one breast). But even taking tamoxifen, which has some potentially serious side effects, or undergoing the even more severe approach of prophylactic mastectomy — in which one or both breasts are surgically removed — doesn’t bring a woman’s risk down to zero, Disis said.

Wearing bras or using antiperspirants can cause breast cancer.
E-mails blaming bras or antiperspirants for the development of breast cancer have been popping up periodically over the past year.

Wendy Potts, helpline manager for the Susan G. Komen Breast Cancer Foundation, often fields questions about these rumors. “People will forward the e-mail myths and ask if they’re true. We’ve been getting the bra one for years and the antiperspirant one for about a year. The Foundation finally had to write a responding to the antiperspirant myth.”

The and the also have addressed this myth in statements on their Web sites.

The bra rumor is based on the hypothesis set forth by a husband-and-wife team of anthropologists a few years ago in the book “Dressed to Kill,” in which they claim bras constrict the lymph system, causing toxins to accumulate in breast tissues, resulting in cancer.

They say this explains the high rate of breast cancer in Western cultures and the low rate in less-industrialized regions of the world, where women are less likely to wear bras.

“Biologically, this is just not a credible hypothesis,” Smith said. “The authors of this hypothesis published it not through the scientific literature but on their own in book form so that it bypassed all the conventional peer-review processes.”

A lack of blood supply or increased pressure is not what causes normal cells to become malignant, Glaspy added. “It is a series of mistakes that are made in the Xeroxing of genetic material when cells divide.”

The antiperspirant myth claims that while deodorant is safe, antiperspirant is the “leading cause of breast cancer.” According to the e-mail, by stopping perspiration, antiperspirant prevents the armpits from purging toxins, which are then deposited in the lymph nodes, where the toxins lead to cell mutations.

Experts, however, beg to differ with the science behind this theory.

“First of all, sweat is not a mechanism for eliminating toxins. That’s why we have kidneys and livers,” Glaspy said. “We wouldn’t need those if sweat did it. Sweat is a cooling mechanism for the body.

“There aren’t toxins or carcinogens in sweat,” Glaspy said. Plus, he added, people in cultures in which antiperspirant had not yet been introduced still developed breast cancer.

“There is no evidence that underwire bras or any kind of undergarment or antiperspirant or anything a woman would put in her armpit would alter breast cancer risk one bit,” he said.

Potts attributes the spread of these online rumors to wishful thinking. “If somebody hears that they can avoid the disease, they’re apt to believe it,” she said. “We’d all like to believe that we could avoid getting breast cancer.”

Only women get breast cancer.
Breast cancer is not exclusively a woman’s disease. It does occur in men, though infrequently; about one out of every 100 breast cancer cases strikes males.

“The overall incidence of breast cancer among men is very, very low,” Smith said. “But this notion that it’s only a woman’s disease has contributed to some men not responding to symptoms.”

Potts says it isn’t uncommon for men to call the Komen Foundation helpline completely unaware of their risk. “We have men that call and have either just heard that men have a slight risk for breast cancer or they’ve just been diagnosed and didn’t realize they could get the disease and have questions,” she said.

Men have breast tissue and they are exposed to some of the same hormones as women, though in much smaller amounts. They also can inherit the BRCA2 mutation that increases their risk as well as that of women.

Men who develop breast cancer are actually more likely to die from the disease than women because they are usually diagnosed at a later stage in the disease. They often aren’t as aware of the symptoms as women, and since mammograms aren’t routinely recommended for men, the earliest forms of the disease are usually not detected in men, according to Disis.

“One of the problems is that women are so mobilized into support groups for the disease and the way men approach having cancer means a lot of times they are left out when it comes to different resources that are available for them in breast cancer as well as clinical trials that will accept men that have breast cancer,” Disis said. “I wish there were more resources that were specific to breast cancers in men.”

Women should avoid mammograms because they cause cancer.
Some experts say that mammograms may slightly increase a woman’s risk of developing breast cancer, but strongly disagree with the implication that women should forgo mammography because of this risk. Most say that the known benefits of mammograms far outweigh the very small potential risk of them causing cancer.

“Theoretically our models tell us that regular exposures to ionizing radiation from medical tests will account for a very small number of new cancers compared with the very, very large number of lives that they’re expected to save,” Smith said. “But this is a theoretical conclusion done from mathematical models. There has been no evidence to associate any increase in breast cancer risk with routine mammography. There have been quite a lot of opportunities in breast cancer screening trials and other studies to see an excess if it were significant. But in fact we are talking about very small numbers per millions of exams.”

Glaspy also believes the benefits of mammography far outweigh the risks. “I don’t think having a mammogram every day would be a good idea but having a mammogram once a year, if it does increase breast cancer risk, it’s a tiny increase — and that is more than made up for by the 30 percent reduction in chances of dying from breast cancer women get.”

Additionally, doctors emphasize that these aren’t our mothers’ mammography machines — there has been a push over the last 30 years to increase image quality and cut radiation dosage.

“Today’s mammograms give a lot less radiation than ones 20 years ago did,” Glaspy said. “We’re now down to levels of radiation with a mammogram where the risk, if there is one, of increasing your chances of breast cancer with a mammogram, are less than or equal to those on taking a cross-continental plane flight, which no one thinks twice about.”

Disis say she thinks this is one of the most dangerous breast cancer myths. “It scares me that people say multiple mammograms can cause breast cancer because right now that is the only tool that we really have to diagnose it early in the stages when its completely treatable rather than having women come in with a big palpable lump at a point where breast cancer has already spread,” she said.

Why so many myths?
Though efforts to educate the public about breast cancer, such as the designation of October as National Breast Cancer Awareness Month, have succeeded in debunking some common myths, many still remain.

“One thing attractive about a lot of myths is they give you a course of action that gets you out of your risk, so if you don’t wear underwear you won’t get breast cancer,” Glaspy said.

He added: “I would only argue that there’s plenty of reason to be comfortable about where we are going with breast cancer. Focusing on what are verifiable facts, we can still get some piece of mind, we don’t need quite as many myths as are out there.”

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