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For women with breast cancer, alcohol consumption and obesity herald a poorer prognosis. In one of only a few studies to evaluate the role of alcohol in breast cancer outcomes, researchers found that imbibing just half a drink per day—or 2 to 3 per week—raised the risk of breast cancer recurrence by 39%. In a second study involving ~19,000 women, body mass index (BMI) ≥25 increased the risk of distant metastasis by approximately 45%, reported speakers at SABCS.
Should patients stop drinking?
Alcohol consumption has been found in several studies to raise the risk of developing breast cancer, but conflicting findings have been reported for its role in survival after a breast cancer diagnosis, said Marilyn Kwan, PhD, Division of Research at Kaiser Permanente in Oakland, California. The LACE study prospectively examined 1898 survivors of early stage breast cancer diagnosed in 1997-2000. Investigators assessed alcohol consumption using a food frequency questionnaire, which was administered an average of 2 years following the initial diagnosis. The study defined a standard drink as 13.7 g (0.6 oz) of alcohol. Half the women reported some alcohol use, with wine being the most prevalent (90%), followed by liquor (43%) and beer (36%). The women reporting alcohol use tended to be younger, white, well educated, and former or current smokers.
“We found that consuming alcohol may negatively affect breast cancer prognosis, especially among postmenopausal women and those with estrogen receptor (ER)—positive tumors,” Kwan said. Compared with little or no alcohol consumption, defined as ≤0.5 g/ day, drinking ≥6 g/day was associated with a 34% increased risk of recurrence overall, a 51% increased risk among postmenopausal women, and a 58% increased risk among women who were overweight or obese. There was a trend toward a doubling in risk in women with ER-positive tumors.
Alcohol consumption was also associated with a 51% increase in the risk of death from breast cancer, but not from other causes, said Kwan. The increased risk was greatest in wine drinkers who reported having ≥2 drinks per day, which raised their risk by 37% compared with women who abstained from alcohol.
Kwan said other large prospective trials must confirm the findings before physicians start recommending that breast cancer patients change their lifestyle. She added that the study does suggest that “after a breast cancer diagnosis, women should consider limiting their consumption of alcohol.” This may especially be advisable, she said, for women who are postmenopausal or overweight.
Obesity linked to earlier deaths
A study from Denmark implicated obesity in poorer outcomes. The retrospective study looked at data for 53,816 women treated for early breast cancer between 1977 and 2006. Long-term followup data were available for 18,967 women.
Compared to those patients with a BMI <25, those with higher BMIs tended to be older and were more often postmenopausal. They also had larger tumors and more grade III tumors, more lymph nodes removed, more positive nodes, and more nodes with invasion into deep fascia.
By univariate analysis, the risk of a locoregional recurrence was not related to BMI. Risk of distant metastases after 3 years of follow-up, however, correlated to increases in BMI after 3 years, and the risk of dying from breast cancer remained elevated for obese women through 30 years of observation, reported Marianne Ewertz, MD, of the University of Southern Denmark. “After adjustments for the effects of other prognostic factors, patients with a BMI >25 had a 42% to 46% increased risk of developing distant metastases within 10 years and a 26% to 38% increased risk of dying from breast cancer 10 or more years after diagnosis,” she reported.
“Within the first 10 years of follow-up, chemotherapy and endocrine treatments were equally effective in lean and obese patients, but after 10 or more years the treatment effect did not last in the obese patients, who had a poorer survival,” Ewertz said. “Adjuvant treatment seems to lose its effect sooner in the obese.”
Moderator praises studies
Michelle Holmes, MD, of Brigham and Women’s Hospital, Boston, Massachusetts, discussed the findings and praised the investigators for conducting well-designed studies to shed light on these issues. “While these are not randomized controlled trials, such trials are unlikely to be conducted on lifestyle factors, and these two studies are as good as it gets,” she said.
The LACE study has the advantage of being based on data from patients enrolled in a health maintenance organization, which offers excellent follow-up for recurrence, she noted. The study also controlled for factors that would predispose women for better survival. The Danish obesity study is the largest study and the one with the longest follow-up (30 years), she said. “It allows for a detailed look at subgroups and confirms what others have reported—that there is an increased risk of breast cancer death for heavy women with breast cancer.”