A US study, published in the Journal of the National Cancer Institute, has confirmed suggestions that certain types of breast cancer are more common among women who regularly drink alcohol.

Scientists at the Fred Hutchinson Cancer Research Centre followed 2,944 postmenopausal women, all of whom took part in the wider Women's Health Initiative study between 1993 and 1998.

All of the women involved in the latest analysis had been diagnosed with invasive breast cancer and the researchers looked at a wide range of data on each of them.

This included details about their tumours, such as whether they originated in the breast ducts (ductal tumours) or milk-producing lobes (lobular tumours) and chemical details about the tumours' sensitivity to the hormones oestrogen and progesterone.

They also examined lifestyle factors, such as the women's self-reported levels of alcohol consumption; family history of diseases; and whether or not they had children.

Analysis revealed a link between alcohol consumption and an increased risk of breast cancer overall. However, drinking was more strongly associated with certain types of invasive breast cancer than others.

For instance, women who had seven or more alcoholic drinks per week were almost twice as likely to develop hormone-sensitive lobular cancer as those who never drank alcohol.

In contrast, there was no statistically significant association between drinking alcohol and risk of invasive ductal cancer.

The findings support previous studies which found a link between alcohol consumption and hormone-positive breast cancers, as well as studies revealing a stronger association between alcohol and lobular cancer than between alcohol and ductal cancer.

The degree of elevated risk did not appear to be affected by the type of alcohol consumed.

Writing in the Journal of the National Cancer Institute, the study authors revealed: "We found that women who drank one or more drinks a 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 per cent of all breast cancers, whereas lobular cancer accounts for only about ten to 15 per cent of cases."

Henry Scowcroft, science information manager at Cancer Research UK, commented: "This new study confirms that breast cancer is more common among women who drink alcohol regularly - and the more they drink the more this risk increases.

"The study also confirms that alcohol increases breast cancer risk by affecting the levels of oestrogen in our bodies. Our researchers have estimated that alcohol is linked to around 5,000 cases of breast cancer every year."

Source: Cancer Research UK