Dueling Docs: Is Drinking Linked to Breast Cancer?

The Issue
Alcohol and the Risk of Breast Cancer

The Facts
Is drinking good for you - or not? Seems that nothing short of Prohibition can put an end to the debate. For years, kicking back some booze seemed positively virtuous: a host of studies show that moderate drinking may ward off heart attack and stroke, and possibly dementia and diabetes.

But before you drink to that, consider whether alcohol may also harm the breast. A report in last month's Journal of the National Cancer Institute suggests that as little as one extra glass of wine, beer or hard liquor a day can increase a woman's odds of developing of breast cancer, a finding that pins alcohol on as many as 11% of all breast cancer cases. The study, which followed more than 1 million British women age 50 to 64 for an average of seven years, is one of the largest and longest on the subject. It is also one of the only to show a breast cancer link with just a small amount of imbibing.

What to do?

Two doctors debate the issue: Naomi Allen, the study's lead researcher and cancer epidemiologist at the University of Oxford and Lisa Schwartz, MD, associate professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice and author of Know your Chances: Understanding Health Statistics (University of California Press; 2008).

The Debate

Dr. Allen:

"Most of the work on the link between cancer and alcohol has been on men who are heavy drinkers. What hasn't been known are the chances of developing cancer for the woman on the street who is only drinking a moderate amount.

"That's what we looked at and we found that for every extra drink a day, a woman's risk of breast cancer goes up by 1.1%. We already knew that by the time a woman is age 75, her risk of breast cancer is 9.5%. Add one glass more of alcohol and that risk increases to 10.6%; two glasses, 11.7%. For every drink you consume, your risk of breast cancer continues to go up."

These are tricky statistics. Allen is talking about the extra drink a day, beyond the amount consumed by the average woman in the first place -- that one who has a 9.5% chance of developing breast cancer by age 75. Still, says Allen "A 1.1% increase above the average risk may sound small, but it translates to 20,000 extra cases of breast cancer a year."

What about all those women in France where breast cancer doesn't appear to be epidemic and who seem to drink wine like it's Coke by the caseload from Costco? "Fact is," says Allen, "there's no real evidence that French women are drinking more than women in the US or UK. In my study, women were drinking an average of one drink a day. Are French women really drinking more? We don't know."

One of the reasons Allen is so convinced of her findings is that there's a plausible explanation. "There is emerging evidence that alcohol increases a woman's blood level of estrogen. High levels of estrogen in the blood are a known risk factor for breast cancer."

Should women stop drinking altogether then? Drinking may still ward off heart disease, but for middle aged women, the odds of developing breast cancer is higher than the odds of suffering a heart attack. Says Allen, "You may be better off not drinking at all, but it's too early to give a precise answer." Then too, Allen's study found a decreased risk of thyroid, kidney and non-Hodgkin's lymphoma among women who drank moderate amounts. "Those cancers are rarer than breast cancer to begin with, but alcohol seemed to lower their incidence."

Dr. Schwartz:

"I think these researchers are making the link between drinking and cancer look scarier than it really is."

Schwartz notes that the researchers compared women in the study to the average woman, whose risk of cancer is 9.5% by the time she is 75.

"We don't even know how much the average woman is drinking in the first place. What's important is to look at what really happened to the women in this study. Let's look at how much they drank in absolute terms and then look at their risk of developing breast cancer over the length of the study."

"When you do that," says Schwartz says

"you find that for an individual woman, the increased chance of breast cancer from modest drinking -if it exists- is actually small. Women who drank 1 or 2 glasses of alcohol a week for an average of 7 years had the same chance of getting breast cancer as women who drank none. Meanwhile, women who drank once a day or every other day--3 to 6 glasses a week--had a 97.9% chance of avoiding breast cancer compared to women who drank one or two glasses a week. They had a 98% chance of avoiding breast cancer. This is really a tiny difference."

She continues: "I think we can be suspicious about whether this study is really true. Meantime, all the other studies show a much smaller risk of breast cancer from alcohol than this one does,"

Another red flag for Schwartz is what she described as "some level of inconsistency. The researchers found that non-drinkers are at a greater risk of all cancers combined. I see this as a potential problem with the results."

"I also worry that what the researchers are observing is not really the effect of alcohol on breast cancer but something about the women in the study. The women were recruited from mammogram screening centers, but we don't know how often these women were screened. Was it every three years, or did some women wait longer? As socio-economic status goes up, screening does, too. As does drinking. And the more screening mammograms you have, the more likely a cancer will be found. So, we don't know if the finding of more breast cancer among the drinkers is because of their drinking or because they are screened more often. That could be an explanation for this phenomenon."

The bottom line, says Schwartz is that "as an individual you want to know what your cancer risk is if you drink alcohol. The researchers in this study made a statistical model that spit something out, but when I look at the numbers, I don't agree with their results."

Comments

[Lesscancer]

Good Post -

Relative to the breast cancer piece of this
I think on so many of these issues Devra Davis PhD, MPH, Director, Center for Environmental Oncology of UPCI http://www.environmentaloncology.org/node/244 I think best sums it as she steps back with a an even wider view in her recent article Breast Cancer and Work: The Case for Prevention

Dr Davis states that in the case of Breast Cancer that only one in ten cases of breast cancer occurs in a woman who has inherited the risk of the disease from either her mother or father.

Identical twins begin life from a single egg, but only one may develop cancer. Dr Davis further explains that this means that most cases come about as a result of things that happen in the course of a lifetime of good and bad exposures. Thus, most cases of breast cancer do not result from inherited defects, but arise as a result of complex interactions that take place over the course of a lifetime between genes and the environments in which women live and work...

Bill Couzens Founder Less Cancer

[Formind]

Did the research cite any subsets within the female population? Any additional profiles /percentages given? Recent studies designed with ethnically-diverse subjects consistently demonstrated quantitative metabolic differences, rates of absorption, inherent biological variances, etc.

Personally, I'll go for the chocolate-covered Dunkin Donut over a daiquiri any day but it would be interesting to know more about the design of this study.

[candyapple2]

As a lay person, its hard to evaluate whether those percentages are really meaningful. The more we research and test, the more we will find things to take note of. At what point to you choose to alter your behavior? Particularly when so many questions are raised about the results, it seems premature to do so in this case.

[JanaNYC]

I can't help but wonder if someday researchers will find that the genetic makeup of the tumor is more of a determining factor in whether alcohol causes a higher incidence of cancer, wherever it's located in the body. Someday tumors will be identified by the cells that comprise them, rather than as breast cancer, lung cancer, etc. At least that's what we hear from some of those doing cutting edge cancer research.

[avicenna]

This has been known for some time - women who drink one alcoholic drink per day are at a increase risk for breast cancer than women who drank none. I'm actually researching the sex difference in liver metabolism - which is part of what accounts for this observation. The enzymes that detoxify drugs, hormones and other biologically active compounds (called the cytochrome p450 enzymes) work differently between men and women - and variations in them are also responsible of the "coffee effect". For some, who can metabolize coffee rapidly, they actually derive the benefits of the antioxidants and polyphenols from the beverage and decrease their risk of disease. For "slow metabolizers" - they are actually at an increased risk of heart attacks for every drink of coffee they take in. This is the same thing that accounts for alcohol - the fact that women who drink keep these detox liver enzymes busy - they are slower at breaking down estrogen in their bodies which leads to an overall greater exposure overtime. This leads to an increased risk of estrogen-dependent cancers.

[Janice Horowitz - Huffpost Blogger]

hi,
Please let me know when you get results from your research. Maybe it's something I can write about. Thanks.
Janice

[katbur2]

While these results may well be the case, I am not in a position to debate them. We are learning more and more that cancer is not just one disease but a variety. So how do we look at a study that says that increasing the amount of alcohol increase the risk of breast cancer. What kind of breast cancer? Estrogen, progesterone or herceptin positive? Node ositive or negative? Ductal in situ, invasive lobular or invasive ductal?

Let me be clear, I am not encouraging women to go out and get drunk on a daily basis but as a young survivor of breast cancer I will encourage all of you to have a good time. To live your life. Eat healthy foods, keep your weight in check, try to exercise. If you have a family history watch what you're doing, get tested more regularly and talk to your doctor. Whether or not you have a second glass of wine is probably not going to be the decision that determines whether you live or die.
Kate@ http://aftercancernowwhat.blogspot.com

[Janice Horowitz - Huffpost Blogger]

Bravo. I couldn't agree w you more. And that last researcher it seems is also in your camp. Thanks for commenting.

[querencia]

What this article does not addres is whether all that screening and the thought forms associated with that very misogenist process, along with the radiation, may also impact the breast cancer rate. It also ignores factors such as whether the wine is produced with pesticides or not, how the women deal with stresss (which affects the immune system) whether they currently or previous have had hormone therapy or used hormone therapy birth control, how often they have orgasms etc. etc. etc. If they conclude that having daily or weekly orgasms increases your chance of cancer too- are you going to abstain? Who wants to be the girl in the bubble? So these kind of studies are just too limited and too easy to tweak the statistics without really finding anything defnitive. Folks- we are all going to die. We take good care of ourselves in the meantime and our body will fight to the last for its viability but trying to control our risk for cancer through mitigating alcohol intake to gain a couple of statistically questionable percentage points, while eating gmo grains, pesticides, meat and dairy products treated with antibiotics is fairly nuts. I eat organic. . When I do die, I will have enjoyed my evening meals (and my marital life) anyhow. A sante!

[Janice Horowitz - Huffpost Blogger]

Interesting thought about the chemicals in wine. I should have posed the question. Next time. Thanks for the thoughtful input.

[Lesscancer]

The EPA, CDC and NIH have long warned of the hazards of pesticides and the known harms to human health, anything from eye irritations to cancer. In this day and age of unprecedented cases of cancer, communities must look to reducing the unnecessary and preventable environmental exposures that have been linked to such illnesses.

Bill Couzens Founder Less Cancer