Cancer
Alcohol linked to increased risk of invasive breast cancer
By David Liu, Ph. D.
Apr 14, 2008 - 10:46:30 AM

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MONDAY April 14, 2008 (foodconsumer.org) -- Intake of even a small amount of alcohol per day increases the risk of invasive breast cancer, according to a new study presented Sunday at the annual meeting of the American Association for Cancer Research in San Diego.

The increase can be particularly significant in the estrogen-receptor (ER+) and progesterone-receptor positive (PR+) breast cancer, which accounts for 70 percent of the most common type of breast cancer.

Many epidemiologic studies have linked alcohol consumption to increased risk of breast cancer.  Laboratory studies have demonstrated that alcohol increases the amount of estrogen metabolites in a woman’s body, which can in turn act as a fuel for hormone-sensitive breast cancer.

At the meeting, two studies were presented, one examining whether the hormone receptor status of the tumor affects the relationship between alcohol consumption and the risk of breast cancer and the second exploring possible mechanisms to explain the increased risk.

For the first study known as the NIH-AARP Diet and Health Study, Dasmine Lew of the U.S. National Cancer Institute and colleagues followed more than 184,000 postmenopausal women for an average of seven years.

They found 70 percent of women in the study drank alcohol with the average daily intake less than one drink a day. They identified 5,461 cases of invasive breast cancer of which 2,391 cases recorded tumor type information, 1,641 ER+/PR+, 366 ER-/PR-, 336 ER+/PR-, and 48 ER-/PR+.

The risk of ER+/PR+ breast cancer was found 51 percent, 32 percent, and 7 percent higher among those who drank three or more glasses of alcohol a day, among those who drank one or two drinks and among those who drank one glass a day respectively, compared to the risk among teetotalers.

The increased risk of invasive breast cancer was observed across different types of alcohol consumed, the NCI team noted.

Lew and colleagues said their analysis could not support a definitive conclusion as to whether alcohol influences development of other breast cancer tumor types. “But we have enough numbers to study alcohol’s influence on ER+/PR+ breast cancer,” Lew said.

The researchers have long suspected that the effect of alcohol is mediated through the hormone-receptors although other mechanisms are also possible.

"Our study at this point provides evidence for the notion that alcohol affects estrogen metabolism, which increases risk of hormone sensitive breast cancer," Lew said. "Still, more study is needed to clarify the effect of alcohol on other tumor types."

The second study showed specific variations within two genes known as ADH1B and ADH1C involved with alcohol metabolism were associated with an increased risk of breast cancer in postmenopausal women.

Teams led by Peter Shields, M.D. at Georgetown University’s Lombardi Comprehensive Cancer Center and Jo Freudenheim, Ph.D. at the State University of New York at Buffalo reported that ADH1B and ADH1C may as much as double the risk of breast cancer in a postmenopausal woman drinker.

"We found that variations in two genes coding for the alcohol dehydrogenase enzyme increase the risk of breast cancer among women who drink," said lead author Catalin Marian, M.D., Ph.D. at Georgetown. "The higher their alcohol consumption, the higher their risk."

The study team analyzed DNA samples taken from 991 women with breast cancer and 1,698 controls. The researchers found variations within the DNA sequences rs1042026 in the gene ADH1B and rs1614972 in the gene ADH1C were linked with an increased risk of breast cancer in postmenopausal women.

Women who had a variant form of the gene ADH1B and also drank alcohol were twice as likely to develop breast cancer as those who abstained, the study showed.

These two current studies are not the first to reveal the association between alcohol consumption and increased risk of breast cancer.  At least more than 1950 studies have been conducted to establish the association between alcohol consumption and breast cancer risk.

Studies also showed the faster a woman metabolizes alcohol, the higher her risk for breast cancer.  In a report published in the April 27 2006 issue of Carcinogenesis, Terry MB and colleagues from Columbia University and Mount Sinai Hospital in Toronto, Canada mentioned moderate alcohol consumption of about 1-2 drinks a day had been associated with a 30- 50 percent increase in breast cancer risk.  Their study also suggested that those who metabolized alcohol quickly have a higher risk of breast cancer than those who digested alcohol slowly.  The rate of metabolizing alcohol depends on the ADH3 genotype.

Alcohol in alcoholic beverages has been recognized by the U.S. government as a human carcinogen for a few years now.  Alcohol consumption has been linked to increased risk not only for breast cancer, but also for a number of other types of cancer.

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