“Moderate” Drinking Is a Risk Factor for Breast Cancer

Alcohol is classified by the World Health Organization and the US Department of Health and Human Services as a carcinogen and is a known risk factor for breast cancer. But, the level of consumption associated with breast cancer has not been well-defined. A prospective cohort study of 105,986 women ages 30–55 years at study entry had alcohol consumption assessed repeatedly over ≤28 years, during which time 7690 cases of invasive breast cancer were diagnosed (>95% confirmed by pathology reports). In adjusted analyses,

• drinking 3–6 drinks* per week was associated with a 15% increase in the risk of invasive breast cancer compared with abstaining (333 versus 281 cases per 100,000 person-years, respectively). Risk was 51% higher at >2 drinks per day and increased 10% for every additional 10 g alcohol consumed per day.

• 10% of all breast cancers were attributable to alcohol, 60% of which were due to drinking <2 drinks per day. Although the risk appeared to be greater for postmenopausal cancers, drinking before and after age 40 was similarly associated with this risk. Heavy drinking episodes only marginally increased the risk already accounted for by average consumption.

Comments:

“Moderate” drinking should be referred to as “low-risk” drinking. Low amounts of alcohol appear to increase the risk of breast cancer, likely related to effects on estrogens. Although the increase might be considered small, it is identical to the decrease in breast-cancer mortality from mammography, the cornerstone of breast-cancer prevention. An accompanying editorial states, “[T]here are no data to provide assurance that giving up alcohol will reduce breast cancer risk,” while the authors recommend weighing the risks against “the beneficial effects [of light to moderate use] on cardiovascular disease.” I find these statements bizarre. We usually do not require evidence that avoiding a carcinogen reduces cancer risk, and we require randomized trial evidence that the benefits of chemopreventive agents outweigh the risks before recommending them. A drug approval agency such as the Food and Drug Administration would not approve a carcinogen a day (even a small amount) to prevent heart disease. Data about alcohol’s risks should be weighed against benefits that individuals perceive (e.g., enjoyment), but not potential disease prevention benefits.

Richard Saitz MD, MPH

Reference:

Chen WY, Rosner B, Hankinson SE, et al. Moderate alcohol consumption during adult life, drinking patterns, and breast cancer risk. JAMA. 2011;306(17):1884–1890.

Narod SA. Alcohol and risk of breast cancer. JAMA. 2011:306(17):1920–1921.