A woman’s history of drinking is directly linked to her chances of developing the most common form of breast cancer and it doesn’t matter what form of alcoholic beverage she prefers, either.  The largest study ever conducted that matches alcoholic consumption with types of breast cancer says that three drinks a day increases the risk of estrogen- and progesterone-positive cancer by as much as 51%.

Jasmine Q. Lew, a University of Chicago medical student and first author of the study, urges women to evaluate other factors associated with breast cancer, including the history of breast cancer within their families, before indulging in excessive alcoholic consumption, especially when undergoing hormone replacement therapy (HRT).  Laboratory studies have proven that alcohol affects estrogen metabolism in such a way that it acts as fuel for a form of cancer that is hormone sensitive.  This hormone-sensitive breast cancer, indicated as ER+/PR+ (estrogen receptor positive/progesterone receptor positive) accounts for about 70% of all cases of breast cancer.

Lew and her fellow researchers reviewed data on 184,418 postmenopausal women collected in the NIH-AARP Diet and Health Study, which began assembling data in 1995.  Study participants reported their alcoholic consumption as less than one drink per day, one to two drinks per, or three or more drinks per day.  After seven years, follow-up studies identified 70% of the women as drinking every day.  Those who drank even moderately faced an increased risk for breast cancer development.

Researchers then isolated 5,461 participants diagnosed with invasive breast cancer of which 2,391 cases were identified by the tumor type as follows:

• 1,641 ER+/PR+
• 366 ER-/PR-
• 336 ER+/PR-
• 48 ER-/PR+

When tumor types were compared with alcohol consumption, research revealed a strong association between ER+/PR+ tumors and alcohol consumption.  For this type tumor alone, study participants who drank less than one drink each day were 7% more likely to develop this type cancer.  Those enjoying one to two drinks each day were 32% more at risk and those who drank three or more alcoholic beverages per day were 51% more likely to develop this form of breast cancer than teetotalers.

The relationship between the other three forms of tumor studied and alcohol consumption were statistically insignificant, as was the form of alcoholic beverage routinely consumed.

The findings of this study were presented at the 2008 annual meeting of the American Association for Cancer Research, which runs from April 12 through 16.