even few drinks a day can b risky

OXFORD, England, Feb. 24 - The link between alcohol and cancer extends even to women who drink in moderation, according to a large British survey.

A history of low or moderate alcohol consumption increased the risk of a half dozen types of cancer as well as total cancer, Naomi E. Allen, D.Phil., of the University of Oxford, and colleagues reported online in the Journal of the National Cancer Institute.

The risk was greatest for breast cancer, which increased by 11 cases per 1,000 to age 75 with every additional drink.

"Although the magnitude of the excess absolute risk associated with one additional drink per day may appear small for some cancer sites, the high prevalence of moderate alcohol drinking among women in many populations means that the proportion of cancers attributable to alcohol is an important public health issue," the researchers said.

Authors of an accompanying editorial said the study clearly demonstrated that no level of alcohol consumption should be considered safe.

The weight of epidemiologic evidence persuaded the International Agency for Research on Cancer to conclude in 2007 that alcohol causes breast cancer in women and cancer of the oral cavity, pharynx, esophagus, larynx, colorectum, and liver in both sexes.

But most of the evidence has come from studies involving men who were heavy drinkers, the authors noted. Little information exists about the cancer risks associated with moderate alcohol intake, typical of most women.

To examine the impact of drinking on cancer risk in women, investigators analyzed data from the Million Women Study, which involved 1.3 million middle-aged women who attended breast cancer screening clinics in England from 1996 through 2001.

In surveys completed at enrollment and 3 years later, participants provided information about weekly alcohol consumption.

Using data from the National Health Service, the authors examined associations between alcohol consumption and the 21 most common types of cancer.

A quarter of the women reported no drinking and 98% of the drinkers consumed fewer than 21 drinks a week. The drinkers consumed an average of 10 g of alcohol (MedPage Today) -- about one drink -- a day.

During 7.2 years of follow-up, 68,775 invasive cancers were diagnosed in the women.

The authors found that every 10 g/day increase in alcohol consumption significantly increased the risk of the following cancers:

• Oral cavity and pharynx (29%, P<0.001>
• Esophagus (22%, P=0.002)
• Larynx (44%, P=0.008)
• Rectum (10%, P=0.02)
• Liver (24%, P=0.03)
• Breast (12%, P<0.001)
• Total cancer (6%, P=0.03)

The risk of several types of aerodigestive cancers was increased significantly in current and ex-smokers who also drank but not in nonsmokers.

The increased risk was similar in women who drank wine exclusively and in those who consumed other types of alcohol.

Increasing alcohol consumption was associated with significant decreases in the risk of thyroid cancer (P=0.005), non-Hodgkin's lymphoma (P=0.001), and renal cell carcinoma (P=0.03).

In their editorial, Michael S. Lauer, M.D., and Paul Sorlie, Ph.D., of the National Heart, Lung and Blood Institute, said the size of the study population strengthens the findings.

Acknowledging that studies have shown cardiovascular benefits associated with moderate alcohol consumption, they said the cancer risk may outweigh those benefits.

"From a standpoint of cancer risk, the message of this report could not be clearer," they said. "There is no level of alcohol consumption that can be considered safe."

The Million Women Study is supported by Cancer Research UK, the Medical Research Council, and the National Health Service.

Neither the authors nor the editorialists reported any conflicts of interest.

Primary source: Journal of the National Cancer Institute Source reference: Allen NE et al. "Moderate alcohol intake and cancer incidence in women." J Natl Cancer Inst. 2009;101:296-305.Additional source: Journal of the National Cancer InstituteSource reference: Lauer MS, Sorlie P. "Alcohol, cardiovascular disease, and cancer: treat with caution." J Natl Cancer Inst. 2009;101:282-283.

Even a Few Drinks a Day Increases Cancer Risk in Women

The study reviewed here strongly suggests that regularly drinking even small amounts of alcohol increases the risk of many types of cancer -- including breast cancer -- in women.

Earlier research has shown a link between drinking large amounts of alcohol and higher breast cancer risk. Most of this earlier research suggested that small amounts of alcohol didn't affect breast cancer risk very much.

Still, based on the results of the study reviewed here, the researchers concluded that there's NO amount of alcohol that's safe when it comes to cancer risk.

The study, called the Million Women Study, had 1.3 million middle-aged women living in England fill out two surveys: one when they joined the study and one 3 years later. The surveys asked the women how many alcoholic drinks they had each week. About 25% of the women didn't drink alcohol. The women who drank alcohol had about one drink per day.

The researchers then looked at the medical histories of the women for the next 7 years to see if there was a link between cancer risk and regularly drinking alcohol. Because the study was so large (more than 1 million women), the results are considered very credible:

• About 69,000 women developed some form of cancer.
• Cancer risk was lowest in the women who didn't drink alcohol.
• Women who drank were more likely to develop several types of cancer, including breast, liver, rectum, mouth, throat, and esophagus compared to women who didn't drink.
• The higher cancer risk was seen even in women who regularly drank only small amounts of alcohol.
• The researchers estimated that each daily drink increases breast cancer risk by about 12%. So compared to a woman who doesn't drink:
  • a woman who has one drink per day has about a 12% higher risk of breast cancer
  • a woman who has two drinks per day has about a 24% higher risk of breast cancer

Researchers don't completely understand why drinking alcohol seems to increase breast cancer risk. Other studies have shown that hormone-receptor-positive breast cancer is the type of breast cancer most affected by alcohol. Estrogen can cause hormone-receptor-positive breast cancer to grow and alcohol can increase the amount of estrogen in a woman's body. This increase in estrogen may be part of the reason for the link between alcohol and breast cancer risk.

It's also worth noting that the women in this study self-reported how much they drank. It's unclear whether the women kept alcohol diaries so they had a written record to refer to or whether they simply relied on memory when filling out the two surveys. Depending on people's memories of what they ate or drank is a common way to do studies like this. Still, people sometimes think they ate or drank less than they actually did, which can influence the results.

The results of this study support the results of many other large studies linking alcohol to breast cancer risk. If you want to do everything you can to lower your risk of breast cancer (or breast cancer coming back), limiting your drinking makes sense. Based on the study reviewed here, drinking any amount of alcohol regularly seems to increase cancer risk.

Regularly drinking alcohol is a habit that often starts in early adulthood. You might want to talk to your daughters, granddaughters, and other young women in your life about the link between alcohol and breast cancer risk.

To learn more about how you can keep your risk of breast cancer as low as it can be, visit the Breastcancer.org Lower Your Risksection.