Alcohol and Hormone Therapy Increase the Risk of Breast Cancer

Abstract & Commentary

Synopsis: The Nurses’ Health Study reports an increased incidence of breast cancer with daily alcohol consumption, hormone therapy, and an additive effect with greater drinking.

Source: Chen WY, et al. Ann Intern Med. 2002;137: 798-804.

Chen and colleagues from the nurses’ health Study examined the self-reported questionnaire data from their prospective cohort. Comparing the results to nondrinkers and nonusers of hormone therapy, key results were as follows:

  Hormone Users Adjusted Relative Risks
For Invasive Breast Cancer
No alcoholic
intake 
< 5 yrs current use 1.45 (1.13-1.86)
  > 5 yrs current use 1.31 (1.05-1.66)
1.5-2.0 drinks daily < 5 yrs current use 2.08 (1.41-3.08)
  > 5 yrs current use 1.99 (1.41-2.79)

An average intake of less than 1 drink daily did not increase the risk of breast cancer. Analyses including carcinomas in situ were similar. Past users of hormone therapy did not demonstrate an increased risk. Risks were similar comparing estrogen alone with users of combined estrogen and progestin, but the numbers of combination users were small.

Comment by Leon Speroff, MD

The increase in risk for breast cancer associated with postmenopausal hormone therapy in this report from the Nurses’ Health Study is essentially the same as that previously reported. The new observation in their cohort of nurses is that drinking 1.5-2 drinks of alcohol per day further increases the risk. Speculation about a possible mechanism focuses on the well-known demonstration that alcohol acutely increases the blood levels of estrogen.

A limitation of the study is that nurses who consumed 1.5-2 drinks daily amounted to about 10% at the beginning of the study in 1982 and decreased to about 7% a decade later. Nevertheless, the conclusions are consistent with other reports in the literature, and they are consistent with the proposed biologic mechanism.

These results do not differ from that recently published by the Women’s Health Initiative. The magnitude of the breast cancer risk is in the same ballpark, and there remains the unanswered question whether the results reflect the effect of hormone therapy on pre-existing tumors. However, the magnitude of the relative risks in the Nurses’ Health Study (as well as their reliability) can be questioned because of possible important differences comparing hormone users and nonusers. Based on previous Nurses’ Health Study publications, the user group differs in several categories that affect the risk of breast cancer. Current hormone users in the study are more likely to have a history of benign breast disease, to be nulliparous, and to have given birth only once or twice. The Nurses’ Health Study investigators have never adequately addressed this potential confounding of their results.

If the Nurses’ Health Study conclusions are correct, the additive effects of hormone therapy and alcohol are a finding that differs with the Women’s Health Initiative. According to the Women’s Health Initiative, hormone therapy did not further increase the risk of breast cancer associated with other risk factors. However, the actual data were not provided and it is not entirely clear that the relationship between alcohol consumption and hormone therapy was adequately examined.

Basically, this report should change our interaction with patients only by further increasing our concern for women who drink alcohol daily and consume more than 1 drink daily.

Dr. Speroff is Professor of Obstetrics and Gynecology, Oregon Health Sciences University, Portland, Ore.