The study reviewed here suggests that drinking even a few glasses of alcohol per week increases the risk of breast cancer coming back (recurrence) in women who've been diagnosed with early-stage disease. These results were reported at the 2009 San Antonio Breast Cancer Symposium.
The results are similar to other studies suggesting that recurrence risk goes up if a woman drinks alcohol. Other research also has shown that the risk of being diagnosed with breast cancer is higher in women who drink alcohol.
Over a period of 8 years, researchers looked at the medical and alcohol consumption records of nearly 2,000 women diagnosed with early-stage breast cancer. About 350 women had a breast cancer recurrence and 332 women died during the 8 years. Not all the deaths were related to breast cancer.
Half of the women were characterized as moderate-to-heavy drinkers, meaning they had at least 3 or more drinks per week. Wine was the most popular alcoholic beverage, followed by liquor and beer.
The researchers looked at both the risk of recurrence and the risk of dying from breast cancer in women who were moderate-to-heavy drinkers compared to women who didn't drink alcohol.
Researchers don't completely understand why alcohol seems to increase the risk of breast cancer recurrence. Other studies have shown that hormone-receptor-positive breast cancer seems to be 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 increase in estrogen may be why there seems to be a link between drinking alcohol and breast cancer recurrence risk.
The bottom line is that we really don't know how much alcohol is safe for breast cancer survivors. If you've been diagnosed with early-stage breast cancer and want to do everything you can to lower your risk of recurrence, limiting how much alcohol you drink seems to make sense. You may even choose to stop drinking alcohol completely. It's also very important not to mix alcohol with some of the medicines you might be taking, such as pain medications.
SAN ANTONIO (MedPage Today) -- Even a few glasses of wine or cocktails a week may increase risk of recurrence for breast cancer survivors, researchers found.
Women who averaged three to four or more drinks per week were 34% more likely to have a recurrence than those who drank less than once a week, according to an observational study led by Marilyn L. Kwan, PhD, of Kaiser Permanente in Oakland, Calif.
Likewise, breast cancer-specific mortality risk rose 51% for the regular drinkers among breast cancer survivors, Kwan's group reported here at the San Antonio Breast Cancer Symposium.
After a breast cancer diagnosis, women who drink alcohol should consider cutting back, they recommended.
This is important news for clinicians because patients often ask how they can personally reduce their risk after successful treatment, commented Jeffrey M. Peppercorn, MD, MPH, of Duke University in Durham, N.C., who was not involved in the study.
"If they want to do everything they can personally do, then lowering alcohol consumption is part of that," he said.
In the general population, alcohol has been linked to elevated risk of developing breast cancer but also to a variety of benefits, when taken in moderation, for cardiovascular, GI, and mental health and even general longevity.
The American Cancer Society says the cardiovascular benefits of moderate drinking may outweigh the risk of cancer for men over age 50 and women over 60.
However, the ACS and the American Heart Association recommend against starting to drink solely to reduce heart disease risk.
Thus, the new results could be consistent with counseling breast cancer patients that "one glass of wine may be okay but keep it at that," Peppercorn said, though he cautioned against overinterpreting the observational data.
Kwan agreed that these women should ask their physicians about individual recommendations involving lifestyle issues, including alcohol.
The reason for the latest finding may be that alcohol increases estrogen levels, according to study discussant Michelle D. Holmes, MD, DrPH, of Brigham and Women's Hospital in Boston.
Because of limited data on how alcohol affects women after breast cancer diagnosis, Kwan's group analyzed findings from the Life After Cancer Epidemiology (LACE) Study, a prospective cohort study of early-stage breast cancer survivors.
The 1,897 participants, diagnosed with early-stage breast cancer between 1997 and 2000, were largely recruited from the Kaiser Permanente Northern California Cancer Registry.
The researchers classified 51% of the women as drinkers, meaning they averaged more than 0.5 g of alcohol per day. The study defined one drink as 13.7 grams.
Most of the drinking done by women in the study involved wine (90%), followed by liquor (43%) and beer (36%).
After eight years of annual follow-up via questionnaire, investigators confirmed 349 breast cancer recurrences and 332 deaths by medical record review.
Drinking did not appear to impact overall mortality (HR 1.19, P=0.22 for trend).
Women whose alcohol consumption was defined as moderate-to-heavy (at least 6 g of alcohol a day, or at least 3 to 4 drinks per week) were at elevated risk of both breast cancer recurrence (HR 1.34, 95% CI 1.00 to 1.82) and death from breast cancer (HR 1.51, 95% CI 1.00 to 2.28) compared with those who drank no more than 0.5 g per day.
The increased risk of recurrence was highest for women who drank two or more glasses of wine a day, while there was no significant risk increase among those who consumed less than three drinks overall per week.
The risk didn't differ by type of alcohol, unlike results of some prior studies evaluating the effects of drinking in other populations for other conditions, though not for breast cancer incidence.
Postmenopausal breast cancer survivors were particularly at risk from moderate to heavy drinking (HR 1.51 versus 1.24 for premenopausal, P=0.03 for trend), as were overweight and obese women (HR 1.58 versus 1.09 for normal weight, P=0.03 for trend).
The researchers cautioned that further prospective studies are needed to confirm the findings.
Peppercorn additionally warned about the barely significant overall hazard ratios and the limitations of self-reporting alcohol intake.
The study could not determine causality, and false associations due to confounding from other factors were possible, he noted.
"Maybe some women who were at higher risk decided that they could drink more," Peppercorn speculated. "Maybe there's an association between being told you have a worse prognosis and deciding that lowering your alcohol intake is not worth it."
Holmes agreed that unresolved confounding is a criticism of all cohort studies, but a randomized trial is unlikely to ever happen.
"This is as good as it gets, and it's pretty good," she concluded.
The study was funded by the National Cancer Institute. The researchers reported no conflicts of interest.
Peppercorn and Holmes reported no conflicts of interest.
Primary source: San Antonio Breast Cancer Symposium Source reference: Kwan ML, et al "Alcohol consumption and breast cancer recurrence and survival among women with early-stage breast cancer" SABCS 2009; Abstract 17.
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