Even Low to Moderate Alcohol Consumption Increases Risk for Cancer in Women

Zosia Chustecka

February 24, 2009

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February 24, 2009 — Even low to moderate alcohol consumption significantly increases the risk for cancer, both overall and at specific sites, in women, according to results from the Million Women Study conducted in the United Kingdom.

The women in the study were middle-aged (median age, 55 years), and 75% said they drank alcohol, consuming — on average — 1 drink per day (10-g alcohol). Very few drank more than 3 or more drinks per day, and there was no difference between wine or other drinks, such as spirits, although most women drank wine.

Each drink significantly increased the risk for cancer, the researchers found.

For such women in developed countries, the researchers estimated a background incidence of 118 cancers diagnosed per 1000 women up to the age of 75 years.

Consuming 1 drink per day increased this to an extra 15 cancers per 1000 women, and 2 drinks a day increased it to an extra 30 cancers per 1000 women, they report. Most were breast cancers, but the risk of cancer was also increased for the liver and rectum, and for the mouth and throat in women who also smoked.

Cancers at these sites have been linked to alcohol in the past, but this study shows that even low to moderate consumption significantly increases the risk, lead author Naomi Allen, DPhil, from Oxford University, in the United Kingdom, told Medscape Oncology.

"From a standpoint of cancer risk, the message of this report could not be clearer. There is no level of alcohol consumption that can be considered safe," say Michael Lauer, MD, and Paul Sorlie, PhD, from the Division of Prevention and Population Sciences at the National Heart, Lung and Blood Institute, in Bethesda, Maryland.

Their comments appear in an editorial published online February 24 with the report in the Journal of the National Cancer Institute.

Change Advice About Alcohol?

These latest "fascinating" findings should give pause for thought, say the editorialists. Although the medical dangers of too much alcohol are well-known and have been known for a long time, in recent years there has been increasing research to suggest that small amounts may be beneficial to cardiovascular health, which has led to some promotion of drinking to maintain heart health.

As an example, the editorialists cite an American Heart Association science advisory about "wine and your heart" (Goldberg IJ et al. Circulation 2001;103;472-475).

"Even if there are modest beneficial cardiovascular effects of alcohol," the editorialists comment, the current report should "remind us that we must consider the broader public-health context."

Among women the major cause of death by far during the middle years is cancer.

"Among women the major cause of death by far during the middle years is cancer," the editorialists point out.

"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," they add.

"It might be reasonable to suspect that many women in the lay public who are asking physicians about any possible safe effects of alcohol are middle-aged," the editorialist write. "For this large group, the only reasonable recommendation we can make is that there is no clear evidence that alcohol has medical benefits."

Lead investigator Dr. Allen told Medscape Oncology that she agreed with this message.

"We found no suggestion of a minimal level below which there is no increase in risk," she said. "The risk of cancer increased proportionately according to the amount of alcohol consumed."

CancerResearch UK, which supported the study, said in a statement: "This latest study shows that even relatively low levels of drinking increase a woman's risk. It is important that women are as well informed as possible so they can take responsible decisions over how much alcohol they drink."

As the study focused solely on the risk for cancer associated with alcohol, Dr. Allen said it was not possible at this time to comment on how this risk would balance against any potential benefits on cardiovascular health.

However, in order to answer this question, her team is now planning to use these same data on alcohol consumption from the Million Women Study to investigate the association with cardiovascular disease, looking at coronary heart disease, stroke, and related events. These results should be out in "the next few years," she said.

Increase in Cancer Overall and at Specific Sites

The study followed 1,280,296 women who attended breast-cancer screening clinics in the United Kingdom from 1996 to 2001. After an average of 7.2 years of follow-up, cancer was diagnosed in 68,775 of these women.

Alcohol consumption was self-reported. The researchers did not use nondrinkers as a reference group, because they suspected that there was "a spuriously high relative risk in this group." The collected data did not differentiate between those who had never drunk alcohol and those who were not drinking now but had done so in the past, and the researchers suspected that many nondrinkers were actually former drinkers who stopped drinking due to illness.

They found an increased risk for cancer in nondrinkers compared with a group who drank 2 drinks a week or less. Dr. Allen explained that when her group examined these cases further, they found that the nondrinkers had a 40% increase in risk for liver cancer and esophageal cancer, both of which have well-known associations with alcohol. She suggested that these may have been cases where women were drinking until they developed problems, such as difficulties with swallowing, and then stopped because they felt unwell.

Hence, the researchers carried out trend analyses of the association between the amount of alcohol consumed and the risk for cancer. All estimates were adjusted for potential confounding factors, including age, smoking, and use of oral contraceptives and hormone-replacement therapy.

Each additional drink regularly consumed per day was associated with 11 additional breast cancers per 1000 women up to the age of 75 years; with 1 additional cancer of the oral cavity and pharynx and 1 additional cancer of the rectum; and with 0.7 each for esophageal, laryngeal, and liver cancers.

The proportion of cancers attributable to alcohol is an important public-health issue.

"Although the magnitude of the excess absolute risk associated with 1 additional drink per day may appear small for some cancer sites," the researchers write, "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."

For example, in the United Kingdom, these estimates suggest that around 13% of cancers of the breast, upper aerodigestive tract, rectum, and liver — that is, 7000 cases annually — can be attributed to alcohol.

This study was conducted in middle-aged women, but other studies conducted in younger women (eg, 20- to 30-year-olds) have shown similar associations, Dr. Allen commented. However, as most of the excess risk was for breast cancer, it is not clear how these results relate to men, she added.

AHA Comment

Asked to comment on the study, an American Heart Association spokesperson cited the association’s position statement on alcohol, which emphasizes that people who already drink alcohol should do so in moderation--one to two drinks per day for men and one drink per day for women.

"Drinking more alcohol increases such dangers as alcoholism, high blood pressure, obesity, stroke, breast cancer, suicide, and accidents," an AHA statement reads. "Also, it's not possible to predict in which people alcoholism will become a problem. Given these and other risks, the American Heart Association cautions people not to start drinking . . . if they do not already drink alcohol. Consult your doctor on the benefits and risks of consuming alcohol in moderation.”

No conflicts of interest were reported.

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

J Natl Cancer Inst. 2009;101:296-305, 282-283.

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