The risk of breast cancer increases two fold in women who have only one alcoholic drink a day, compared to those who abstain completely, reports a new US study.
To understand how alcohol may influence sub-types of breast cancer, Christopher I. Li, and colleagues at Fred Hutchinson Cancer Research Center conducted an observational study of a subset of patients in the Women's Health Initiative (WHI) study, conducted between 1993 and 1998, which included 87,724 postmenopausal women aged 50-79 years.
The researchers looked at the following data from the 2,944 women in the WHI study who developed invasive breast cancer: tumor subtypes and hormone status, alcohol consumption, demographic and lifestyle characteristics, family history of diseases and reproductive history.
Women were categorized as those who never drank, those who formerly drank and those who currently drank. Drinkers were grouped into six categories according to the average number of drinks per week, starting from less than one drink per week to more than 14 drinks per week.
The researchers found that alcohol use is more strongly related to the risk of lobular carcinoma than ductal carcinoma, and more strongly related to hormone-receptor- positive breast cancer than hormone-receptor-negative breast cancer.
"We found that women who drank one or more drinks per day had about double the risk of lobular type breast cancer, but no increase in their risk of ductal type breast cancer," the authors said.
"It is important to note that ductal cancer is much more common than lobular cancer accounting for about 70 percent of all breast cancers whereas lobular cancer accounts for only about 10-15 percent of cases," they added.
The study has been published August 23 online in The Journal of the National Cancer Institute.