Update on alcohol and breast cancer

Summary: the most extensive study to date reveals a modest but significant increase in breast cancer risk from alcohol consumption that should be balanced against the risk for cardiovascular disease.An important study just published in JAMA (the Journal of the American Medical Association) goes further than all previous studies in examining the association between modest alcohol consumption over extended periods of time and breast cancer. The authors state:

"Multiple studies have linked alcohol consumption to breast cancer risk, but the risk of lower levels of consumption has not been well quantified. In addition, the role of drinking patterns (ie, frequency of drinking and “binge” drinking) and consumption at different times of adult life are not well understood."

This new study is important because it followed women over a longer period of time and included for factors that can also alter breast cancer risk such as pregnancy, ionizing radiation, etc. in 105,986 nurses over 28 years as the authors set out to...

"...evaluate the association of breast cancer with alcohol consumption during adult life, including quantity, frequency, and age at consumption."

Their data show that the amount of alcohol rather than frequency of drinking is associated with breast cancer risk, and that age doesn't matter:

"During 2.4 million person-years of follow-up, 7690 cases of invasive breast cancer were diagnosed. Increasing alcohol consumption was associated with increased breast cancer risk that was statistically significant at levels as low as 5.0 to 9.9 g per day, equivalent to 3 to 6 drinks per week. Binge drinking, but not frequency of drinking, was associated with breast cancer risk after controlling for cumulative alcohol intake. Alcohol intake both earlier and later in adult life was independently associated with risk."

Analysis of their data also revealed a trend for a 10% increase in breast cancer risk for each 10 gram increase in alcohol consumption. The mechanism is not certain, but because the greatest impact was on hormone receptor-positive breast cancer it is likely related to the tendency for alcohol to increase circulating levels of estrogen. The authors conclude:

"Low levels of alcohol consumption were associated with a small increase in breast cancer risk, with the most consistent measure being cumulative alcohol intake throughout adult life. Alcohol intake both earlier and later in adult life was independently associated with risk."

As with everything else in medicine, the information needs to be considered in the context of each woman's individual health and family history, including the balance of risks for cancer and heart disease.