All alcohol consumption linked to breast cancer risk

One of the largest individual studies of the effects of alcohol on the risk of breast cancer shows that it makes no difference whether a woman drinks wine, beer or spirits (liquor).

It is the alcohol itself (ethyl alcohol) and the quantity consumed that increases breast cancer risk. In fact, the increased breast cancer risk from drinking three or more alcoholic drinks a day is similar to the increased breast cancer risk from smoking a packet of cigarettes or more a day, according to Kaiser Permanente researchers Yan Li, MD, PhD and Arthur Klatsky, MD.

"Population studies have consistently linked drinking alcohol to an increased risk of female breast cancer, but until now there has been little data, most of it conflicting, about an independent role played by the choice of beverage type," said Klatsky, who is presenting these findings on September 27th at the European Cancer Conference (ECCO 14) in Barcelona, Spain.

Li, a Kaiser Permanente oncologist, Klatsky, an investigator with the Kaiser Permanente Division of Research in Oakland, CA and their Kaiser Permanente colleagues studied the drinking habits of 70,033 multi-ethnic women who had supplied information during health examinations between 1978-1985. By 2004, 2,829 of these women were diagnosed with breast cancer. In one analysis, researchers compared the role of total alcohol intake among women who favored one type of drink over another with women who had no clear preference. In another analysis, researchers looked at the possible independent role of frequency of drinking each beverage type. Finally, they examined the role of total alcohol intake, comparing it with women who drank less than one alcoholic drink a day.

The study found there was no difference between wine, beer or spirits in the risk of developing breast cancer. Even when wine was divided into red and white, there was no difference. However, when researchers looked at the relationship between breast cancer risk and total alcohol intake, they found that women who drank between one and two alcoholic drinks per day increased their risk of breast cancer by 10 percent compared with light drinkers who drank less than one drink a day. The risk of breast cancer increased by 30 percent in women who drank more than three drinks a day.

Results were similar when researchers looked at groups stratified by age and ethnicity. "Statistical analyses limited to strata of wine preferrers, beer preferrers, spirits preferrers or non-preferrers each showed that heavier drinking -- compared to light drinking -- was related to breast cancer risk in each group. This strongly confirms the relation of ethyl alcohol to increased risk," said Klatsky.

"A 30 percent increased risk is not trivial. To put it into context, it is not much different from the increased risk associated with women taking estrogenic hormones. Incidentally, in previous research completed at Kaiser Permanente, we have found that smoking a pack of cigarettes or more per day is related to a similar (30 percent) increased risk of breast cancer," Klatsky said.

Although breast cancer incidence varies between populations and only a small proportion of women are heavy drinkers, Dr Klatsky said that a 30 percent increase in the relative risk of breast cancer from heavy drinking might translate into approximately an extra 5 percent of all women developing breast cancer as a result of their habit.

Other studies, including research from the same authors, have shown light-moderate alcohol drinking can protect against heart attacks, but Klatsky said that different mechanisms were probably at work.

"We think that the heart protection benefit from alcohol is real, and is probably derived largely from alcohol-induced higher HDL ('good') cholesterol, reduced blood clotting and reduced diabetes. None of these mechanisms are known to have anything to do with breast cancer. The possible but unproven additional coronary benefit from drinking wine (red or white) may be related to favorable drinking patterns common among wine drinkers or to the favorable traits of wine drinkers, as evidenced by other United States and Danish studies," Klatsky said.

Klatsky said that all medical advice needed to be personalized to the individual. "Our findings provide more evidence for why heavy drinkers should quit or cut down."

The Kaiser Permanente research group has been involved in studies of alcohol drinking and health for more than three decades, including in the area of heart disease. Kaiser Permanente is uniquely positioned to conduct such research because investigators have access to data about a large, multi-ethnic population with a variety of drinking habits.