Alcohol may influence breast cancer recurrence

NEW YORK (Reuters Health) - Among women who survive early-stage breast cancer, some who make a habit of having a few drinks per week could face a greater risk of a recurrence than survivors who abstain, a new study suggests.

The study, which followed 1,900 women treated for early-stage breast cancer, found that while the large majority did not suffer a recurrence over the next seven years, the risk was relatively greater among those who said they had at least three or four alcoholic drinks per week - particularly if they were older or obese.

Compared with abstainers, the drinkers overall were 35 percent more likely to have a recurrence and 51 percent more likely to die of breast cancer during the study period.

The findings, reported in the Journal of Clinical Oncology, add to a conflicting body of research into whether moderate drinking may shorten the lives of women with a history of breast cancer.

They also point to a rather complex relationship between alcohol intake and breast cancer survivors' long-term prognosis.

When the researchers divided the women into subgroups, they found that moderate drinking showed a stronger relationship with the risk of recurrence and breast cancer death among postmenopausal women (51 percent increased risk), compared with younger women.

And when the study patients were separated according to body weight, the link was stronger among overweight and obese women (60 percent increased risk), versus those with normal weights.

What's more, drinking habits were not linked to the women's overall death rate during the study period -- only their death rate from breast cancer.

That finding, researchers say, might reflect the fact that moderate drinking may reduce the risk of heart disease, the number-one killer of U.S. women.

So what should a woman with a history of early-stage breast cancer do?

"The most important advice I can give a breast cancer patient is to talk with their clinician about any lifestyle changes they are considering after being diagnosed with breast cancer," said study leader Dr. Marilyn L. Kwan, a research scientist at Kaiser Permanente in Oakland, California.

"She can then fully evaluate the risks and benefits of consuming alcohol, and at what amount," Kwan told Reuters Health in an e-mail.

She noted that the results cannot be generalized to women treated for more advanced cancer since the study did not include such patients.

The findings are based on 1,897 women treated for early breast cancer who were followed for just over seven years. During that time, 293 women had a cancer recurrence and 273 died due to breast cancer or other causes.

Those numbers are in keeping with national averages. An estimated 207,000 new cases of breast cancer will be diagnosed in the U.S. this year, with an expected 85 - 90 percent 5-year survival rate for cases detected in early stages.

In the current study, 478 of the women were considered "regular drinkers," reporting the equivalent of three to four alcoholic beverages a week; 78 of those women, or 16 percent, had a breast cancer recurrence, and 42 (9 percent) died from the disease. In comparison, 14.5 percent of the 939 non-drinkers had a breast cancer recurrence, and just under 8 percent died of the disease.

When Kwan's team factored in a number of other variables -- like age, body weight at the time of diagnosis and treatment type -- regular drinkers were 35 percent more likely to have a recurrence than abstainers. They also had a 51 percent greater chance of dying from breast cancer (which would increase an average absolute 5-year mortality risk of 10 percent to 15 percent).

The bulk of that increased risk fell on postmenopausal and obese women, however. There was some evidence of increased risk of recurrence or breast cancer death among premenopausal and normal-weight women who regularly drank, but the findings were not statistically significant, which means they could have been due to chance.

However, Kwan said she wants to "emphasize" that regular drinking was associated with a poorer breast cancer prognosis in the entire study group, and that the relationship may be stronger among postmenopausal or overweight women.

"These stronger associations perhaps indicate that women in these subgroups may be more susceptible to the effects of alcohol," Kwan said.

The findings may help explain why past studies have come to conflicting conclusions as to whether drinking is associated with long-term survival among women treated for breast cancer, according to an editorial published with the study.

Of 10 studies on the question published between 1991 and 2008, eight showed no relationship between drinking habits and survival, notes Dr. Michelle D. Holmes of Brigham and Women's Hospital and Harvard Medical School in Boston.

But in five of those eight studies, the researchers looked at deaths from all causes, Holmes points out. The current findings suggest that there may, in fact, not be an association between drinking and all-cause mortality, but with breast cancer deaths specifically.

So the question of whether breast cancer survivors can drink moderately has no "clear-cut yes or no" answer, according to Holmes.

"Moderate consumption of alcohol," she writes, "is likely to increase a woman's risk of dying as a result of breast cancer while decreasing her risk of dying as a result of heart disease."

The decision on drinking, Holmes concludes, "is dependent on each woman's evaluation of and comfort level with those risks."

Researchers believe that regular drinking may contribute to breast cancer in some women by boosting blood levels of estrogen, which can help feed tumor growth. On the other hand, moderate amounts of alcohol may have a number of benefits for the heart, such as increasing "good" HDL cholesterol, curbing body-wide inflammation and reducing the likelihood of blood clots.

There are, however, many ways other than moderate drinking to help cut the risk of heart disease -- including regular exercise and a healthy diet, not smoking, and controlling heart risk factors like high blood pressure, high cholesterol and diabetes.

SOURCE: http://link.reuters.com/nuq72p Journal of Clinical Oncology, online August 30, 2010.