Breast Cancer and Alcohol Consumption
Does alcohol consumption affect the risk of breast cancer?
Yes. In most but not all research studies, drinking alcohol has been associated with a modest increase in the risk of breast cancer. However, scientists are not exactly sure how alcohol affects risk. Alcohol may act as a co-carcinogen -- an agent that makes it easier for cancer-causing substances to enter and damage individual cells. Also, alcohol may temporarily increase the concentration of estrogens that circulate in the blood. This is significant because estrogen increases the frequency with which cells in the milk glands of the breast divide and grow. The fact that the concentration of estrogen is higher in women who drink alcohol could mean that there are more cell divisions. The more times a cell divides -- or copies itself -- the greater the likelihood that a cancer-causing mutation will occur because of an error in copying.
How much does alcohol intake affect the risk of breast cancer?
For premenopausal women, the difference between non-drinkers and moderate drinkers is minimal but noticeable. Of every 10,000 average 40-year-old women who rarely or never drink alcohol, about 145 (a little under 1.5%) will have breast cancer within the next 10 years. Of every 10,000 similar women who drink three to six alcoholic beverages in a typical week, around 150 (about 1.5%) will get breast cancer within the decade. This difference of five women per 10,000 per decade for non-drinkers versus moderate drinkers is not extremely large. However, for women whose risk of breast cancer is already higher than normal because of other factors, a reduction in the frequency of drinking alcohol might have a noticeable effect on risk.
Does the risk associated with alcohol consumption decrease or increase with age?
Generally, the risk of breast cancer that is associated with alcohol consumption decreases as women enter menopause. Alcohol does not appear to affect the blood level of estrogens of women whose levels are already low (that is, most postmenopausal women).
The situation is different for women who are undergoing hormone replacement therapy (HRT). Women undergoing HRT appear to be more sensitive to alcohol and their hormone levels rise after drinking. Does this difference in estrogen levels for the combination of alcohol and HRT have anything to do with the actual risk of breast cancer? The only studies that have asked this question say that it does. Women who took HRT but did not drink and women who drank but do not take HRT did not appear to have any increased risk of breast cancer.
Does the quantity of alcohol consumed matter?
The study data obtained on this issue describe women who drink moderately. It is more difficult to say whether the risk of breast cancer is affected by heavy drinking, because very few women who drink at heavy or abusive levels have volunteered for research studies on breast cancer. Studies performed at autopsy provide a clue. Women who die young are frequently the victims of accidents or violence, and these deaths are referred to a medical examiner. One study of deaths referred to a medical examiner evaluated the breast tissue of women who abused alcohol and had died of causes other than breast cancer before the age of 55. The results indicated that premenopausal women who drink large quantities of alcohol have a higher incidence of breast cancer. Specifically, 30% of the women had a carcinoma in situ (a precancerous condition sometimes called stage 0 breast cancer). This remarkably high rate of undetected breast lesions is one more reason -- out of many -- to avoid heavy drinking during the premenopausal years, when estrogen levels are already high.
