A panel of international experts concludes in a new report that smoking and secondhand smoke increase the risk of breast cancer in women.
The Canadian Expert Panel on Tobacco Smoke and Breast Cancer Risk says it reviewed dozens of recent studies on various aspects of smoking and breast cancer before drawing its conclusions.
"Based on the weight of evidence from epidemiologic and toxicological studies and understanding of biological mechanisms, the associations between active smoking and both pre and postmenopausal breast cancer are consistent with causality," the panel writes in its report.
The experts also say the link between second-hand smoke and breast cancer in premenopausal women who have never smoked "is consistent with causality."
But they say there is not yet enough evidence to say whether second-hand smoke causes postmenopausal breast cancer.
Nor is there yet enough information to estimate how many cases of breast cancer or breast cancer deaths could be attributed to smoking and second-hand smoke. The panel recommends further research in this area.
The panel was convened by the Ontario Tobacco Research Unit, an affiliate of the Dalla Lana School of Public Health, University of Toronto.
The link between breast cancer and tobacco smoke has, until recently, been inconclusive, with some studies showing increase in risk and others not.
Dr. Anthony Miller, associate director of research at the school of public health, says he hopes the conclusions he panel has come to will remind women of yet another one of the hazards of smoking.
"It is important from a public health perspective to get the message out to the public, and young women in particular, that available evidence shows that both active smoking and exposure to passive smoke increase the risk of breast cancer," said Miller.
He also wants the message to be heard by parents, friends and others who might be exposing young women to second-hand smoke.
