A recent study assessed the association between moderate alcohol consumption and breast cancer risk in the Women’s Health Study (United States, 1992-2004). During an average of 10 years of follow up, 1,484 cases of total breast cancer (1,190 invasive and 294 in situ) were documented among 38,454 women who, at baseline, were free of cancer and cardiovascular disease and provided detailed dietary information, including alcohol consumption, for the preceding 12 months.
Higher alcohol consumption was associated with a modest increase in breast cancer risk; the multivariable relative risks for ≥ 30 g/day of alcohol vs. none were 1.32 for total breast cancer and 1.43 for invasive breast cancer. An increased risk was limited to estrogen receptor (ER) and progesterone receptor (PR) positive tumors; the multivariable relative risks for an increment of 10 g/day of alcohol were 1.11 for ER+PR+ tumors, 1.00 for ER+PR tumors, and 0.99 for ERPR tumors. The association also seemed strongest among those taking postmenopausal hormones currently, but the test for interaction was not significant. The findings from this prospective study suggest that moderate alcohol consumption increases breast cancer risk.
Comments by R. Curtis Ellison There have been many reports suggesting a modest increase in breast cancer risk for women who consume alcohol, with just over 10% increase for women averaging about 1 drink/day. This report shows similar increases as most other reports, with the findings being positive only for tumors that are estrogen and progesterone positive, suggesting that alcohol may have an effect on cancer risk primarily through hormonal changes. This study shows the effects of alcohol on breast cancer risk to occur only among current users of postmenopausal hormone use. Unlike previous studies, this study did not show any protective effect of folate intake on the association. As for beverage-specific effects, when adjusted for all beverages consumed, the relative risk was > 1.0 for beer, white wine, and liquor, but was 0.99 for red wine, suggesting that there may be no increase from red wine.
Source: Zhang SM, Lee I-M, Manson JE, Cook NR, Willett WC, Buring JE. Alcohol consumption and breast cancer risk in the Women’s Health Study. Am J Epidemiol 2007; electronic publication DOI: 10.1093/aje/kwk054