Breast Cancer Health Center

Second Breast Cancer: 3 Lifestyle Risks

Sept. 8, 2009 -- Being obese, drinking seven or more alcoholic beverages per week, and smoking may make a second breast cancer more likely, a new study shows.

The study, published in the advance online edition of the Journal of Clinical Oncology, focused on women with estrogen receptor-positive (ER-positive) breast cancer. Most breast cancers are ER-positive, which means the tumors grow when exposed to the hormone estrogen.

Data came from more than 1,000 Seattle-area breast cancer patients, including 365 women who developed a second breast cancer in their opposite breast.

The women were interviewed about their smoking and drinking; their BMI (body mass index) was noted in their medical records.

The odds of developing a second breast cancer in the opposite breast were greater for obese women, for women who drank at least seven alcoholic beverages per week, and current smokers.

"We found that obese women had a 50% increased risk, women who consumed at least one alcoholic drink per day had a 90% increased risk, and women who were current smokers had a 120% increased risk of developing a second breast cancer," researcher Christopher Li, MD, PhD, says in a news release.

Li is an associate member of the public health sciences division of the Fred Hutchinson Cancer Research Center in Seattle. He and his colleagues recently published a separate report about tamoxifen and the odds of developing a second breast cancer.

Li's new paper doesn't show the absolute risk of developing a second breast cancer in the opposite breast, and it doesn't include women with ER-negative breast cancer. It also doesn't prove that losing weight, quitting smoking, or cutting back on alcohol would have made a difference.

However, extra weight and alcohol use have been linked to breast cancer risk in other studies. Smoking hasn't been firmly established as a breast cancer risk, but Li's team calls that biologically plausible.

Li and colleagues also found that among women who drank at least seven alcoholic beverages per week, the odds of developing a second breast cancer in the opposite breast were about seven times higher if those women were current smokers.

An editorial published with the study asks, "So does this mean that women should be advised to lose weight and avoid alcohol and smoking after breast cancer diagnosis in order to reduce the risk of a second primary breast cancer?"

The editorialist -- Jennifer Ligibel, MD, of the Dana-Farber Cancer Institute and Harvard Medical School -- points out that losing extra weight and quitting smoking are healthy changes to make. But Ligibel says that because moderate alcohol use may have heart health benefits, it's "premature" to advise breast cancer patients to quit drinking entirely.