Study: Alcohol and breast cancer risk in African American women

IN-DEPTH REVIEW OF RESEARCH

Study background:

Breast cancer survival rates differ between non-Hispanic White women and AA women, who are almost twice as likely to die of breast cancer by age 50.  This difference may be due in part to the stage of cancer at diagnosis and the higher rates of triple-negative breast cancer in Black women.  Because breast cancer survival rates are worse for AA women, and most breast cancer risk factors have been identified by studying White women, it is important to better understand the risk factors that contribute to increased risk in African American women.

Reports from The World Cancer Research Fund/American Institute for Cancer Research Continuous Update Project (CUP) reveals how much daily drinking might impact breast cancer risk for both premenopausal and postmenopausal women. “Sipping an average of 10 grams of alcohol a day—equivalent to a small glass of wine, an 8-ounce beer or 1 ounce of hard liquor—is associated with a 5% increased breast cancer risk in premenopausal women and 9% increase in postmenopausal women”, said Dr. Anne McTiernan, a lead author of the new report and a cancer prevention researcher at the Fred Hutchinson Cancer Research Center in Seattle. The CUP report showed a significantly greater risk in breast cancer with increasing alcohol consumption for both groups, leading the CUP to conclude that alcoholic drinks probably contribute to risk of premenopausal breast cancer and may contribute even greater risk of postmenopausal breast cancer. However, the CUP report was based on data from studies of women in Europe and North America and risks were not broken down by race.

The results of another study (which is the featured study of this review) by Lindsay A. Williams colleagues were published in Cancer Epidemiology, Biomarkers & Prevention in May 2017. Researchers analyzed questionnaire data on alcohol intake and breast cancer diagnoses from 22,338 women from the African American Breast Cancer Epidemiology and Risk (AMBER) consortium. 

Researchers of this study wanted to:

Determine if alcohol consumption increased breast cancer risk among African American women. 

Population(s) looked at in the study:

This analysis included 22,338 African American women from the AMBER consortium, which consists of four large epidemiologic studies on breast cancer: the Carolina Breast Cancer Study, the Black Women's Health Study, the Multiethnic Cohort Study and the Women's Circle of Health Study. Each study measured alcohol intake via questionnaires. The current analysis included 5,108 cases of invasive breast cancer and 17,230 controls, of whom approximately 35% were current drinkers at interview. Forty-five percent of participants were never drinkers and 20.8% were past drinkers.

Study findings: 

The association between the number of alcoholic drinks per week (dpw) and breast cancer was estimated using statistical analysis, adjusting for any potential confounder (factor that may affect the relationship between variables being studied, i.e. oral contraceptive use). Results were analyzed by breast cancer subtype: 

• Compared to light drinkers, women who reported drinking 14 or more dpw were 33% more likely to develop breast cancer.
  • Women who drank 7 or more dpw were almost 40% more likely to develop triple negative disease.
• "Never drinkers," who made up 45% of all women in this study, were 12% more likely to develop breast cancer than light drinkers.
• Risk associated with alcohol intake did not vary significantly by oral contraceptive use, smoking status or menopausal status.

Women who previously drank alcohol but later stopped had lower risk than women who reported that they recently drank alcohol, suggesting that women may be able to reduce their breast cancer risk by reducing their alcohol consumption.

Limitations:

The analysis included relatively few women who drank heavily, making the findings less statistically significant. In addition, researchers did not have information on reasons for alcohol abstinence, which could shed light on the elevated risk observed among never drinkers in this study. The results of this study were derived by pooling data from 4 individual studies, and thus may be affected by differences between the studies. Finally, the results are likely impacted by recall bias (a participant’s ability to remember their alcohol consumption).

Conclusions:

Among African American women, drinking 7 or more alcoholic drinks per week was associated with an increased risk of breast cancer, regardless of breast cancer subtype. According to the senior researcher, Melissa A. Troester, PhD, the results of this study indicate that the same risk factors that have been documented in previous research apply to Black women as well. "Alcohol is an important modifiable exposure, whereas many other risk factors are not," she said. "Women who are concerned about their risk of breast cancer could consider reducing levels of exposure."

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Posted 10/27/17