One drink per day can increase breast cancer risk by 5%

A new review of research that looks at the relationship of alcohol consumption and breast cancer has been published in the journal Alcohol and Alcoholism. The analysis found that low level or moderate drinkers – one drink per day – had a 5% increased risk of breast cancer. Heavy alcohol consumption, defi ned as three or more drinks a day, was found to have a 40-50% increased risk of breast cancer. Overall, alcohol drinking accounts for roughly 5% of breast cancers in Northern Europe and North America and up to 10% in countries such as Italy and France, where drinking alcohol is common among women.

In Europe and the USA, breast cancer is the most common cancer in women. Several population studies have also shown that women have a high prevalence of light drinking. This represents a major health issue in terms of breast cancers and the western world. Alcohol consumption has been acknowledged as a risk factor for the development of cancer in various organs of the body for quite some years and an association between alcohol and breast cancer has been established since the 1980s. The review of research conducted by Helmut K. Seitz and Carlo La Vecchia et al, and published today in Alcohol and Alcoholism, is entitled ‘Epidemiology and Pathophysiology of Alcohol and Breast Cancer: Update 2012’. The review analyses epidemiological data on the relationship of alcohol and breast cancer, looking at the possible mechanisms of alcohol-mediated breast cancer development.

Light alcohol consumption

When analysing the effects of light alcohol drinking, the authors reviewed research published before November 2011 via a literature search from MEDLINE, ISI Web of Science and EMBASE. In total, 3431 research papers were retrieved from the literature search. Of these, 113 papers reporting breast cancer risk estimates for light drinkers were included in the meta-analysis. The analysis included 44,552 cases in the reference category of nondrinkers and 77,539 cases in the light drinking category. 51% of studies were from North America, 38% from Europe, 6% from Asia and 10% from other regions. The meta-analysis of these studies reported a modest but significant association between light drinking and breast cancer. The estimate was based on the results of more than one hundred studies and found a small increase in risk, in the order of 5%, with the association between light drinking and breast cancer.

Dose-risk

The review carried out by Seitz and La Vecchia et al also found that each increased alcohol consumption increases the risk of breast cancer. This analysis showed a trend risk that was highly significant and there is consistent evidence for a positive dose-risk relation between alcohol and breast cancer.

Heavy Alcohol consumption

The largest collection of studies connecting the risk of breast cancer to alcohol was based on high level consumption of alcohol and cancer risk. The results indicated a 40-50% elevated risk of breast cancer in women consuming three or more drinks a day.

Hormone related mechanisms

Cancer of the female breast is slightly different to other body organ cancers as even small doses of alcohol can stimulate breast cancer development. As alcohol consumption might affect the risk of cancer through hormone related mechanisms, the review published today in Alcohol and Alcoholism particularly looked at the association between alcohol consumption and the risk of breast cancer through hormone-related mechanisms such as estrogen receptor (ER) and progesterone receptor (PR) status. Seitz et al found that there was significant research to suggest that alcohol consumption increased the risk of all ER+ tumours by 27% and placed a 14% risk for all ER- breast cancers for the highest vs lowest level of alcohol drinking. Subsequent investigations by the team found further support for a stronger association between heavy alcohol consumption and ER+ breast cancers.

Studies investigating the mechanisms of ethanolmediated breast cancer are rare and information is limited. However, a promotional effect of estrogens on breast tissue has been observed and since alcohol consumption causes elevated estrogen concentrations, it has been speculated that the carcinogenic effect of alcohol is mediated, in part, by estrogens. Seitz and La Vecchia et al discuss a number of study examples that provide further evidence on the role of estrogens in ethanol-mediated breast cancer and possible carcinogens for the breast. The observation that several studies support the hypothesis that alcohol is more strongly related to ER positive than ER negative breast tumours underlines the pathogenic role of estrogens in alcohol mediated breast cancer.

“Epidemiology and Pathophysiology of Alcohol and Breast Cancer: Update”, Seitz, La Vecchia, et al, Alcohol and Alcoholism, doi: 10.1093/alcalc/ags011