According to researchers at the Fred Hutchinson Cancer Research Center, older women who have smoked a pack of cigarettes a day for at least 11 years face a 30 percent to 40 percent increased risk of developing breast cancer as compared to women who have never smoked. To make it worse, women smokers who are on hormone-replacement therapy, HRT, increase their odds of getting breast cancer by 110 percent, and more than double that of women who have never smoked or taken HRT.

"We know that smoking is associated with a lot of diseases, from lung cancer to heart disease, but the association with breast cancer is still somewhat controversial," states Christopher I. Li, M.D., Ph.D, assistant professor of epidemiology at the University of Washington School of Public Health and Community Medicine. "Certainly, the association between smoking and breast cancer is nowhere near as strong as the association between smoking and lung cancer, but breast cancer may be another disease to add to the long list of serious health issues related to smoking." Based on this study, researchers indicate that once a woman stops smoking, within about 10 years of quitting, her risk of breast cancer falls back to that of a woman who has never smoked.