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 percent more likely to have a recurrence than those who rarely, if ever, drank, according to an observational study led by Dr. Marilyn Kwan of Kaiser Permanente in Oakland, Calif.
Likewise, mortality risk rose 51 percent for the heavier drinkers among breast cancer survivors, Kwan's group reported here at the San Antonio Breast Cancer Symposium.
After a breast cancer diagnosis, women should consider cutting back, they recommended.
Patients do often ask how they can personally reduce their risk after successful treatment, commented Dr. Jeffrey Peppercorn of Duke University in Durham, N.C.
"If they want to do everything they can personally do, then lowering alcohol consumption is part of that," said Peppercorn, who was not involved in the study.
In the general population, alcohol has been linked to elevated risk of developing breast cancer but benefits, when taken in moderation, for cardiovascular, some GI, and mental health and even longevity.
The American Cancer Society says that 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 cautioning against overinterpreting the observational data.
But 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 had been diagnosed with early-stage breast cancer between 1997 and 2000 and were largely recruited from the Kaiser Permanente Northern California Cancer Registry.
The researchers classified 51 percent of the women as drinkers, averaging more than 0.5 g of alcohol per day. Most of the drinking done by women in the study involved wine (90 percent), followed by liquor (43 percent) and beer (36 percent).
After eight years of annual follow-up via questionnaire, 349 breast cancer recurrences and 332 deaths were confirmed by medical record review.
Drinking didn't appear to impact overall mortality.
Women who drank at least 6 grams of alcohol per day -- the equivalent of at least three to four drinks per week, considered moderate to heavy drinking -- were at elevated risk of both breast cancer recurrence and death compared with those who drank no more than half a gram per day.
The increased risk of recurrence was highest for women who drank two or more glasses of wine a day, without a significant risk among those who drank less than three drinks overall per week.
But the risk didn't differ by type of alcohol, unlike findings in some prior studies that evaluated the effects of drinking in other populations, and for conditions other than breast cancer incidence.
Postmenopausal breast cancer survivors were particularly at risk from moderate to heavy drinking as were overweight and obese women.
The researchers cautioned that further prospective studies are needed to confirm the findings. Also, 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."