Long-term smoking increases the risk of breast cancer in older postmenopausal women by up to 40 percent, according to a report in the October issue of Cancer Causes and Control.

“Smoking appears to confer a modest elevation in breast cancer risk,” Dr. Christopher I. Li from Fred Hutchinson Cancer Research Center, Seattle, told Reuters Health. “Certainly this relationship is not as strong as the relationship between smoking and lung cancer or smoking and heart disease, but breast cancer may be another disease to add to the long list of diseases associated with smoking.”

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.