Unlike earlier studies comparing those who ever smoked with those who never smoked, Li and colleagues assessed the relationships between various measures of cigarette smoking and the risk of invasive breast cancer among women 65 to 79 years of age.

Ever smokers were 30 percent more likely to develop breast cancer, the authors report. Current smoking was more strongly associated than former smoking with breast cancer.

Smoking for 40 years or longer increased the risk of breast cancer by 40 percent, the results indicate, and there was a suggestion that the younger women started smoking the greater their risk of breast cancer.

"No single epidemiologic study stands alone, but based on recent studies there is a growing body of literature suggesting that cigarette smoking is associated with a modest risk of breast cancer," Li concluded. "Additional work is needed to further characterize what aspects of smoking are particularly related to risk."

"Our study focused exclusively on older postmenopausal women 65-79 years of age." Li added. "Thus, these results may not be generalizable to premenopausal women or to younger postmenopausal women."

SOURCE: Cancer Causes and Control October 2005.