The journal Alcohol and Alcoholism has published a new review of studies that have researched the association between alcohol consumption and breast cancer. The findings revealed that the risk of breast cancer rises by 5% for low level or moderate drinkers, i.e. women who have one drink per day, whilst the risk for those who consume three or more drinks daily (heavy consumption) is 40-50% higher.

In Northern Europe and North America, about 5% of breast cancers are due to alcohol consumption, whilst in Italy and France, where alcohol consumption is more common amongst women, 10% of breast cancers are due to drinking alcohol.

Breast cancer is the most common cancer amongst European and American women. Numerous population studies have demonstrated that light drinking is very common amongst women and that the risk of associated breast cancer is a major health issue in the western world.

Scientists have known about the association between alcohol and breast cancer since the 80s; they have long known that alcohol consumption is also a risk factor for the development of cancer in various organs of the body.

Helmut K. Seitz and Carlo La Vecchia and team decided to conduct a review 'Epidemiology and Pathophysiology of Alcohol and Breast Cancer: Update 2012' that analyzed epidemiological data of the link between alcohol and breast cancer and searched for potential mechanisms of alcohol-mediated breast cancer development.

They reviewed literature published prior to November 2011 by searching databases, such as MEDLINE, ISI Web of Science and EMBASE, and found a total of 3,431 research papers, of which 113 included breast cancer risk estimates for light drinkers.

They established that overall, the studies included 44,552 non-drinkers (reference group) and 77,539 participants who were light drinkers. The geographical location of the studies revealed that 51% of the studies were conducted in North America, 38% in Europe, 6% in Asia and 10% from other regions.

According to the study's meta-analysis, which was based on the findings of over 100 studies, there was a modest, yet important link between light drinking and breast cancer, with a 5% higher risk to light drinkers compared with those who were abstinent.

Seitz and La Vecchia's findings also showed that each higher level of alcohol consumption increases the risk of breast cancer. The findings revealed a highly important progressive upward trend in risk together with consistent evidence.

The largest amount of research material was based on the relationship between high-level alcohol consumption and cancer risk, with findings suggesting that women who consume three or more drinks a day have an elevated breast cancer risk of 40-50%.

Unlike other cancers, breast cancer development can be stimulated even by small doses of alcohol. Given that alcohol consumption may affect the risk of cancer through hormone related mechanisms, the researchers specifically examined the link between alcohol consumption and the risk of breast cancer through hormone-related mechanisms like estrogen receptor (ER) and progesterone receptor (PR) status.

They discovered that a substantial amount of research indicates that alcohol consumption increased the risk of all ER+ tumors by 27% and posed a 14% risk for all ER- breast cancers in women with the highest alcohol consumption compared with those consuming the lowest level. The researchers discovered during later evaluations that their findings supported those of other studies, which demonstrated that the association between heavy alcohol consumption and ER+ breast cancers was substantially higher.

With regard to ethanol-mediated breast cancer, the scientists note that few studies have been conducted and that there is only limited information available. They state that previous studies have observed a promotional effect of estrogens on breast tissue, and given that alcohol consumption causes elevated estrogen concentrations, there have been speculations that the carcinogenic effect of alcohol is partly mediated by estrogens.

The team discussed various study examples in terms of estrogen's evidential role in ethanol-mediated breast cancer and possible carcinogens for the breast, and observed that several studies support the belief that alcohol is more strongly related to ER positive than to ER negative breast tumors, which highlights the pathogenic effect of estrogens in alcohol mediated breast cancer.

Written by Petra Rattue