Research Links Smoking, Breast Cancer
Women who smoke cigarettes have an increased risk of getting breast cancer if they carry a hobbled version of a key protective gene, researchers reported Tuesday.
The work, which contradicts previous studies finding no link between smoking and breast cancer, suggests that at least some of the puzzling rise in breast cancer in the past few decades may be due to increased smoking among women. The connection has been hidden, the researchers propose, because other studies didn’t take genetic factors into account.
The critical gene, called NAT2, helps neutralize toxins and cancer-causing chemicals, including some present in cigarette smoke. About half of white women, and a smaller percentage of blacks and Asians, inherit a relatively weak version of the gene. For them, smoking a pack or more of cigarettes a day quadruples the risk of getting breast cancer, according to a report in today’s Journal of the American Medical Assn.
By contrast, women with a potent version of the detoxifying gene had no increase in breast cancer no matter how much they smoked.
“Experiments with animals and on cultured cells suggested tobacco smoke can cause breast cancer,” said Peter G. Shields of the National Cancer Institute, who led the study with Christine B. Ambrosone of the National Center for Toxicological Research in Jefferson, Ark. “Knowing that, it was very puzzling that tobacco was not looking like a risk factor for breast cancer in women. So we wondered, are there some who are susceptible and some who are not?”
That is exactly the case for post-menopausal women, according to the study of 631 women, done in collaboration with researchers at the State University of New York at Buffalo. NAT2 and smoking had no effect on breast cancer risk for women before menopause, but the researchers warned that a link may appear later since cancer can take decades to develop.
Breast cancer incidence has been increasing for the past two decades in the United States. Some of the rise has been linked to improved diagnosis. There are also theories that some of the increase may be caused by such factors as increased fat in the diet and changes in childbearing patterns. But no one has been able to account for all of the increase.
