Nov. 1, 2005 -- Drinking alcohol has been shown to increase breast cancer risk, but new research suggests that this risk may be confined to a particular type of tumor.
In a study that included almost 52,000 postmenopausal women in Sweden, moderate alcohol consumption was found to raise the risk of estrogen receptor-positive (ER-positive) breast cancers. Estrogen receptor-positive breast cancers grow when exposed to the hormone estrogen. Roughly six out of 10 breast cancers are ER-positive.
Women who drink alcohol and take hormone replacement therapy may be at particularly high risk for developing estrogen receptor-positive tumors, the researchers suggest. The findings are published in the Nov. 2 issue of the Journal of the National Cancer Institute.
"It appears from the results of this study that the increase in risk is greatest for women who drink alcohol and take hormone replacement therapy," researcher Alicja Wolk, DMSc, tells WebMD. "This needs to be confirmed, but it may be that women who take hormones should not drink."
Alcohol, Breast Cancer Link
The evidence linking alcohol and breast cancer is strong. One of the largest studies found that women who drank less than one alcoholic beverage a day had a 30% increased risk of dying from breast cancer when compared with women who never drank.
But it hasn't been clear if the risks associated with drinking alcohol varied by tumor type. To address this question, Wolk and colleagues at Stockholm's Karolinska Institute examined alcohol use over a decade among 51,847 postmenopausal women living in Sweden.
By mid-2004, more than 1,200 women in the study were diagnosed with breast cancer. Of these women, data were available on estrogen-receptor status in 1,188 women. Drinking alcohol was associated with an increased risk of developing ER-positive tumors, but no such association was seen among women with ER-negative tumors (tumors that are not affected by estrogen).
Because daily drinking is unusual among older women in Sweden, the women in the study who drank the most still averaged less than one alcoholic beverage a day, Wolk says.
When compared with women who didn't drink, these heaviest drinkers had a higher risk of developing estrogen receptor-positive tumors.
Women who drank the most and also had a history of hormone use had 3.5 times the risk of developing estrogen-receptor positive cancers as nondrinkers who never took hormones.
Weighing the Risks
The findings suggest that alcohol and hormone therapy act more strongly together to promote ER-positive breast cancers. But Wolk acknowledges that there are still many unanswered questions about the association.
It was not clear how long the women in the study had taken hormones, how recently they had taken them, or which combination of hormones they took. Wolk says that information about total duration of alcohol use was not gathered. Also, Wolk reports that other studies have not demonstrated a similar association between alcohol and ER-positive breast tumors.
Heather Feigelson, PhD, tells WebMD that the association makes sense because alcohol use and hormone treatment have independently been linked to an increase in ER-positive breast cancers.
She recommends that postmenopausal women discuss their individual risks with their doctor when weighing whether to have an occasional drink. On the plus side, moderate drinking -- defined as one drink or less a day -- has been shown to help protect against heart disease and is suspected of reducing the risk of dementia.
But for women with other risk factors for breast cancer, such as obesity or a family history of breast cancer, the risks of moderate drinking may outweigh the benefits.