Smoking causes lung cancer and is implicated in a dozen other cancers, but scientists have generally dismissed its importance in breast cancer, saying it plays little role, if any.
Now, a Canadian panel of experts is challenging the widely held view.
In a report issued Thursday, the panel asserted that evidence from new studies strongly suggests that smoking increases the risk of breast cancer and warned that girls and young women faced special risks from exposure to smoke. For them, even exposure to secondhand smoke during this critical period of development may increase the risk of breast cancer later in life, the report said.
The report found strong evidence that secondhand smoke contributed to premenopausal breast cancer but did not find enough support to say it increased the risk of post-menopausal breast cancer.
The perspective is a sharp dissent from the consensus among most scientists that there is not enough consistent evidence to determine whether smoking plays a causal role in breast cancer. The International Agency for Research on Cancer said in a recent report that it found little or no link between active smoking and breast cancer, and the surgeon general's office said in 2006 that there was insufficient evidence to say secondhand smoke caused breast cancer.