Alcohol: the link between hormone replacement and breast cancer risk

Abstract

Many women avoid or discontinue hormone replacement therapy due to the fear of breast cancer. They have read studies linking hormone use with increased breast cancer incidence. The link between alcohol use and breast cancer risk, in contrast, is at least as strong as that of hormone replacement therapy (HRT), yet little publicity has reached practicing physicians or patients. A new study by Ginsburg, suggests that women who use hormone replacement therapy experience an elevation in estradiol levels exceeding the ovulatory range (>300 pg/ml) with prolonged elevation for four hours, after consumption of a moderate amount of alcohol (2 to 4 ounces or .07 grams/kg). This provides a plausible explanation for the observation of increased breast cancer among women who drink alcohol regularly and suggests that a synergism between the two products may be possible. All of the epidemiologic data to date would suggest than an exposure threshold exists for hormone therapy or alcohol use. Existing literature was evaluated to identify studies that simultaneously measure alcohol and HRT exposure in relation to breast cancer incidence.Two epidemiologic studies analyzed both exposures together. The adjustment for alcohol intake in HRT users by Kaufman eliminated any breast cancer risk associated with HRT (Relative Risk: 0.9, 95% Confidence Interval: 0.7–1.1). By subdividing the Iowa Women’s Health Study Cohort, Gapstur found that breast cancer risk was confined to women who used HRT and reported drinking at least 5 grams of alcohol per day. While more study is appropriate, these data are reminiscent of the link that was ultimately identified between the combination of oral contraceptives and smoking on arterial thrombosis. Alcohol and hormone exposure together may act synergistically to create increased breast cancer risk.Given the prolonged elevation of estradiol levels in women who use hormones and consume moderate amounts of alcohol, new guidelines should be established to counsel women who choose to use HRT. They should be informed about the effect of moderate alcohol intake. More importantly, the women who choose to avoid alcohol while they use hormones can be reassured that there is little evidence to suggest that their risk of breast cancer is increased in any way.