Breast-feeding protection extends to hereditary cancer

Journal of the National Cancer Institute 2004; 96: 1094-98

Examining whether the protection against overall breast cancer afforded by breast-feeding also applies to the hereditary forms, BRCA1 and BRCA2.

Breast-feeding may lower the risk of breast cancer among women carrying the BRCA1 tumor suppressor mutation, research suggests.

While several studies indicate that breast-feeding lowers the odds of breast cancer, overall, the impact on hereditary breast cancer is not known, note H. Jernstom (Lund University Hospital, Sweden) and colleagues.

To address this issue, they conducted a case-control study of 3959 women with BRCA1 or BRCA2 mutations, including 1927 with invasive breast cancer while the remainder had no such disease. All the participants were surveyed about their pregnancy and breast-feeding histories.

Among women with BRCA1 mutations, the risk of developing breast cancer fell by an odds ratio of 0.98 for each month of breast-feeding reported. Moreover, those who breast-fed for 1 year or longer were significantly less likely to develop the disease than those who had never breast-fed, with an odds ratio of 0.55. No such association was noted, however, among women with BRCA2 mutations.

Although the sample of women with BRCA2 mutations was too small to preclude a modest association with breast-feeding, the authors nevertheless speculate: "The difference between women with BRCA1 and BRCA2 mutations may reflect underlying differences in the pathogenesis of cancers associated with the two genes."

Posted: 27 July 2004

Breast-feeding cuts cancer risk

Risk of breast cancer halved for some women, study says

Elizabeth Hodgson 
National Post

July 20, 2004 - It’s a small study dealing with only a small percentage of women. But its message is anything but trivial. The study, published today in the Journal of the National Cancer Institute, says breast-feeding reduces a woman’s risk of getting breast cancer by as much as 50% if she has a genetic predisposition to getting the disease.

“This little study highlights in a larger way the importance of breast-feeding,” said Shail Verma, a medical oncologist with the University of Ottawa’s integrated cancer program. “The bigger picture is that breast-feeding is good for all women.”

The study found breast-feeding for one year or longer cuts the risk even further.

“It’s been known for some time that breast-feeding protects against breast cancer,” said Dr. Steven Narod at the Centre for Research in Women’s Health at the University of Toronto, who led the study.

“Generally the magnitude of the risk reduction is not that great. Breast-feeding for one year might reduce the average person’s chance from 8% to 6%. So if the average woman decides to have a baby just to protect against cancer, that suggests an exaggerated concern for her mortality.”

The key is a genetic mutation known as BRCA1. Women who carry it “have an unusually high risk of getting the disease,” Dr. Narod said. “If they breast-feed, that risk goes down by half. That’s a real slice in risk reduction. Pregnancy becomes a genuine motive for longevity.”

Over the course of a lifetime, 8% of all women will get breast cancer. Of these, only 5% to 10% will have a hereditary form of the disease. The new findings are important because among those with the BRCA1 mutation, 80% will develop breast cancer.

There is no definitive answer as to why breast-feeding offers this protection. Cancer researchers have a few different theories. Perhaps fat-soluble carcinogens and pollutants are not stored as efficiently in lactating breasts. There is also evidence to suggest breast-feeding causes physical changes in breast cells that may make them more resistant to the mutations that can lead to cancer.

But the most compelling theory has to do with how pregnancy and breast-feeding reduces exposure to the female hormone estrogen.

“There are lots of risks for getting breast cancer,” Dr. Verma said. “One is to carry the genetic mutation. The other is related to endocrine, or hormonal, causes. A major concern is for women who have overly long exposure to estrogen: women who menstruate early and reach menopause late. Getting pregnant and breast-feeding when a woman doesn't menstruate, gives the breasts a break from that estrogen exposure.”

Then there are the BRCA1 mutation carriers. Dr. Narod says those who carry the mutation are inclined to a more aggressive cancer that is not as estrogen sensitive. The question is, how do you know whether you carry the gene?

Family history, Dr. Narod said, will give some pretty good clues. “Is there a history? If so, then the doctor should order testing. There are many women in the population who don't know they carry the gene. They don't have a dramatic family history so they haven't been tested.”

While this is a cause for concern, Dr. Narod is not yet advocating blanket testing. “The decision of whether or not to get tested is a complicated one. I would say that every woman should have access to the test if she’s concerned,” he said. “Once we’ve established that someone is a carrier, that makes it much easier to counsel them ... so that they're limiting their risk.”

The dramatic decline in cancer incidence among breast-feeding women with the BRCA1 gene does not appear to apply to carriers of the other breast cancer gene known as BRCA2. Studies have shown that alterations in this gene are associated with a higher risk of ovarian cancer in women and colon cancer in men.

“Breast-feeding seemed to have little effect on the long-term health of BRCA2 carriers,” Dr. Narod said. “Why that is, I’m not sure. It may be because we had such a small sampling of them.”

Dr. Verma says this study -- as well as other research looking at the relationship between breast cancer and breast-feeding -- make sense from an epidemiological standpoint. “In countries where we see high birthrates ... in places like the Philippines and Southeast Asia, we see low numbers of breast cancer,” Dr. Verma said. “Nature seems to be telling women that getting pregnant is healthy.”

China produces further evidence of the strong link between pregnancy and protection from breast cancer.

“We would expect to the same low rates of the disease here as we’ve seen in places like the Philippines,” Dr. Verma said. “But ever since they started restricting the number of children allowed, the numbers have gone up.”

It might turn out that childbearing and breast feeding have a greater bearing on whether a woman develops breast cancer than environmental factors, such as pollution, diet, smoking and alcohol.

According to the U. S. National Institute of Environmental Health Sciences , pesticides and other chemicals called environmental estrogens for the way they imitate the female sex hormone, have been under suspicion for years. While one preliminary finding out of Mount Sinai School of Medicine in New York found breast cancer patients had significantly higher levels of DDE, the major break-down product of DDT, no significant association was found with PCBs -- the acronym most bandied about in news reports about toxins and disease.

Additional studies are underway to explore links between pesticides and breast cancer, as well as possible links between the disease and air pollutants, electric and magnetic fields and municipal waste. But the latest study is putting breast feeding back in the spotlight.

Dr. Verma hopes to see a decline in breast cancer numbers now that breast-feeding has become fashionable again for European and North American women.

ADULTS TURN TO BREAST MILK TO EASE EFFECTS OF CHEMOTHERAPY

By Michael Day, Health Correspondent, telegraph.co.uk

Adult cancer patients are taking breast milk in an attempt to to boost their immune systems and reduce the side effects of chemotherapy. A milk bank in California has quietly supplied 28 adult patients in the past four years with donated breast milk.

The Mothers' Milk Bank, one of six in the United States, distributes the milk mainly to premature and low-birth-weight babies but also gives it to adults with a doctor’s prescription.

Cancer specialists in Britain and America were sceptical about the treatment last night, saying that there was little or no hard evidence that it worked. Some of the patients - who drink several ounces of milk a day to ease the ravages of their drugs - said, however, that it had led to big improvements in their general health, and had a powerful anti-cancer effect.

One recipient, Howard Cohen, a computer consultant from Palo Alto, said that his twice-weekly "smoothies" made with breast milk and fruit had helped put his prostate cancer into remission and allowed him to avoid more invasive treatment, such as surgery.

Mr Cohen first took breast milk after he was diagnosed in 1999. His wife read an article about Swedish research on breast milk and cancer cells. A friend who was breast-feeding at the time gave him some of her milk, and Mr Cohen found that his levels of prostate-specific antigen, a warning sign for prostate cancer, dropped back to normal.

His urologist was sceptical but not opposed to Mr Cohen’s self-treatment so long as it had no adverse effects.

Mr Cohen has undergone regular blood tests and screenings in the past two-and-a-half years and there have been no signs of cancer, though his doctor has pointed out that some prostate cancers grow so slowly that it is possible that the breast milk made little or no difference.

He dismissed concerns that drinking breast milk could even be harmful. "You give this stuff to newborn babies,'' Mr Cohen said. "It can't be toxic.''

Breast milk’s benefits for babies are well-documented. Research shows that it helps fight infection, improves immune system function, increases intelligence and combats obesity in later life. Little research has, however, been carried out on the medicinal effects for adults.

In 1995 Swedish researchers, whose work caught Mr Cohen’s attention, isolated a protein in mothers' milk that seemed to kill cancer cells in a test tube and are still trying to develop a drug that takes advantage of that protein.

Many doctors remain sceptical about the value of breast milk for adults, however. They point out that many chemicals will kill cancer cells in a test tube without having a hope of becoming viable treatments.

Dr Michelle Melisko, a consultant oncologist at the University of California-San Francisco, said that mothers' milk was probably unlikely to harm her patients but she did have some concerns.

Some viruses could be passed through breast milk - a potentially serious threat to patients whose immune systems have been weakened by cancer treatments - and she had advised them against using it.

"I’d say the same thing I say to all my patients who want to do alternative things: I don't know how it’s tested,'' Dr Melisko said.

Dr Margit Hamosh, however, a biochemist and human breast milk specialist at Georgetown University, said that breast milk contained compounds "that might definitely help in people who have compromised immune systems."

David Kerr, the professor of clinical pharmacology and cancer therapeutics at Oxford University, said: "This is quite bizarre, completely anecdotal and probably complete bunkum.

"It probably won't do any harm but it’s unlikely to do any good either.

"People with cancer and their families of course want to leave no stone unturned when it come to looking for a cure, and who am I to stand in their way?

"I do warn, however, that there are many charlatans out there. And I think there are several rules to stick by: the product should not cost an arm and a leg; it shouldn't do undue harm, and it shouldn't interfere with the conventional treatments."