Research has consistently shown that regularly drinking alcohol – even as little as one drink per day -- increases a woman’s risk of breast cancer.
It's not clear why drinking alcohol increases breast cancer risk. Many studies have shown that hormone-receptor-positive breast cancer is most affected by alcohol. Estrogen can cause hormone-receptor-positive breast cancer to grow, and alcohol can increase the amount of estrogen in a woman's body. This estrogen increase may partly explain the link.
A new study wanted to know if drinking alcohol before or after being diagnosed with breast cancer affected survival rates. The results seem to suggest that drinking didn’t affect breast cancer survival. Women who drank alcohol after being diagnosed also were less likely to die of heart disease compared to women who never drank. Still, there are some issues with the study. You shouldn’t start drinking or drink more because of the results.
The study was published online on April 8, 2013 by the Journal of Clinical Oncology. Read the abstract of “Alcohol Consumption Before and After Breast Cancer Diagnosis: Associations With Survival From Breast Cancer, Cardiovascular Disease, and Other Causes.”
To look at whether drinking before diagnosis affected survival, the researchers looked at information from nearly 23,000 women in the Collaborative Breast Cancer Study (CBCS). The women, ages 20 to 79, were from New Hampshire, Massachusetts, and Wisconsin. When the study started, the researchers interviewed the women on the telephone and asked them how much and how often they drank over the course of their lives, up to being diagnosed with breast cancer. The researchers also asked the women about other breast cancer risk factors, including childbearing and menstrual history, family history of cancer, exercise habits, height and weight, and hormone replacement therapy use.
To look at whether drinking after diagnosis affected survival, the researchers invited women in the CBCS to participate in another study on survival, the Collaborative Women’s Longevity Study, after the CBCS was done. Nearly 5,000 women agreed to be in this new study. The researchers had the women fill out a questionnaire that was similar to the one used in the CBCS on how much and how often they drank after being diagnosed. The women completed the questionnaire 3 to 9 years after they were diagnosed.
The women were followed for about 11 years after they were diagnosed. During that time, 7,780 women died:
- 3,484 died from breast cancer
- 1,531 died from heart disease
- 2,765 died from other causes
Of the 22,890 women who completed the questionnaire on drinking before diagnosis:
- 4,396 (19%) said they never drank
- 11,497 (50%) drank one to two drinks per week
- 3,583 (16%) drank three to six drinks per week
- 1,647 (7%) drank seven to nine drinks per week
- 1,767 (8%) drank 10 or more drinks per week
Compared to women who didn’t drink before they were diagnosed, women who did drink were more likely to be younger, to smoke, to have a healthier weight, and to have more education.
The researchers found that women who reported drinking moderately (three to six drinks per week) had slightly better breast cancer survival than women who reported never drinking.
Of the 4,881 women who completed the questionnaire on drinking after diagnosis:
- 1,140 (23%) said they never drank
- 2,232 (46%) drank one to two drinks per week
- 790 (16%) drank three to six drinks per week
- 305 (6%) drank seven to nine drinks per week
- 414 (9%) drank 10 or more drinks per week
Compared to women who didn’t drink after they were diagnosed, women who did drink were more likely to be younger, have gained weight after diagnosis, have more education, and have had a mammogram before the study started.
The researchers found no difference in survival between women who drank after diagnosis compared to women who didn’t drink after diagnosis. Women who drank more after diagnosis were less likely to die from heart disease than women who didn’t drink.
While the results of this study seem positive, there are several things to keep in mind before you start making toasts to your health:
- The women in the study had to remember how much they drank both before and after they were diagnosed. It’s extremely likely that many of the women didn’t correctly remember how much they drank. Especially when they had to remember how much they drank decades before they were diagnosed. It’s hard enough to remember what you had for dinner two weeks ago, let alone how many drinks per week you had 20 years ago.
- This study was an observational study. This means that the researchers just observed what happened to the women. The women weren’t randomly assigned to have a certain number of (or no) drinks per week. It may be that the women who drank moderately before or after diagnosis also had other healthy lifestyle habits (healthy diet, regular exercise, good sleep habits). So we can’t say that the better survival for both breast cancer and heart disease was because of the drinking. It could be that the two things just happened to occur in the same people.
- While few other studies have looked at breast cancer survival and drinking, many large studies have linked alcohol and breast cancer risk. Many of these studies suggest that drinking any amount of alcohol regularly seems to increase breast cancer risk.
If you want to do everything you can to lower your risk of breast cancer (or breast cancer coming back), drinking two drinks or fewer per week makes sense.
Breastcancer.org President and Founder Marisa Weiss, M.D., discusses how she unwinds without alcohol after stressful days in her Dec. 1, 2011 Think Pink, Live Green Expert Column.
To learn more about how you can keep your risk of breast cancer as low as it can be, visit the Breastcancer.org Lower Your Risk section.