Alcohol was established as a carcinogen in 1987, with a causal relationship between alcohol and breast cancer being acknowledged in 2007. Research conducted as recently as 2014 yielded convincing evidence that alcohol increases the risk of breast cancer. However, controversy exists regarding a link between light drinking and breast cancer. This review examines three areas of study -- one, the biological pathways of alcohol-linked breast cancer; two, the epidemiological risk relationship between drinking and breast cancer; and three, the global burden of breast cancer incidence and mortality that is attributable to drinking -- with a focus on light drinking.
The authors addressed the relationship between light drinking and breast cancer systematically. The review showed that drinking, even at low levels, increased the risk of breast cancer. First, a review and summary of the literature on the biological mechanisms by which alcohol affects the risk of breast cancer showed that alcohol affects breast-cancer risk through the alteration of hormone levels and the associated biological pathways, carcinogens generated during the metabolism of ethanol, and the inhibition of the one-carbon metabolism pathway. Second, all but two of 15 meta-analyses on the risk relationship between drinking -- including light drinking -- and the risk of breast cancer showed a dose-response relationship between drinking and the risk of breast cancer. Finally, an estimate of the burden of alcohol-attributable breast cancer incidence and mortality by means of a Population-Attributable Fraction methodology (using data on alcohol consumption from the Global Information System on Alcohol and Health, and data on cancer incidence and mortality from the GLOBOCAN database) showed that an estimated 144,000 breast-cancer cases and 38,000 breast-cancer deaths globally in 2012 were attributable to alcohol, with 18.8% of these cases and 17.5% of these deaths affecting women who were light drinkers. The authors of the review conclude that, due to this strong relationship, and to the amount of alcohol consumed globally, the incidence of and mortality from breast cancer caused by alcohol consumption in general and caused by light alcohol consumption are large.
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