Alcohol increases the risk of lobular and hormone receptor-positive breast cancer, but not necessarily invasive ductal carcinomas, according to a study published August 23 online in The Journal of the National Cancer Institute.

Although alcohol intake is an established risk factor for overall breast cancer, few studies have looked at the relationship between alcohol use and breast cancer risk by subtype of breast cancer. While some studies have shown alcohol use is more strongly related to risk of hormone receptor-positive (estrogen receptor and/or progesterone receptor-positive) breast cancer, not many have looked at breast cancer risk by histology, or whether a tumour is ductal - in the milk ducts - or lobular - in the milk-producing lobules.

To understand how alcohol may influence sub-types of breast cancer, Dr 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: tumour subtypes and hormone status, alcohol consumption, demographic and lifestyle characteristics, family history of diseases and reproductive history. Women were categorised 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. These results confirm previous findings of an association of alcohol consumption with hormone-positive breast cancer risk, as well as three previous case control studies that identified a stronger association of alcohol with lobular carcinoma. The risks observed did not vary by the type of alcohol women consumed.

The authors write, "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. 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."

The study's primary limitation, the authors say, is that alcohol usage was only assessed at the beginning of the study, so the researchers had no information on womens' past alcohol usage, nor their subsequent usage.

Source: The Journal of the National Cancer Institute