Research Panel Reports Link Between Smoking, Breast Cancer

A report released on Thursday by a panel of U.S. and Canadian experts disputes a long-held view among scientists that smoking does not increase the risk of breast cancer in women, the New York Times reports. The panel, which was funded by the Public Health Agency of Canada, included 10 breast cancer and public health experts from Canada and the U.S. The report summarizes the panelists' review of newer studies that have been released in the past six or seven years, an analysis method that panelists said helped to distinguish differences between women who had never been exposed to smoke and those who had, either by smoking themselves or through secondhand smoke.

In its report, the panel said that evidence from new studies suggests that smoking increases the risk of breast cancer and that young women and girls face special risks from exposure to smoke. The panel noted that even secondhand smoke exposure during adolescence could increase the risk of breast cancer occurring later in life, the Times reports. The report cited several newer studies that suggest women who start smoking when they are young increase their risk of breast cancer by 20% and that many years of heavy smoking could increase the risk by up to 30%. The panelists did not attempt to quantify how many excess breast cancers are caused by exposure to smoke. Although the report found strong support that secondhand smoke added to premenopausal breast cancer, there was insufficient evidence to conclude that it increased the risk of postmenopausal breast cancer, the Times reports.

The report is "a sharp dissent" from the common belief among scientists that there is too little consistent evidence to determine whether smoke has a causal role in breast cancer, the Times reports. For example, a 2004 report by the International Agency for Research on Cancer found little or no link between breast cancer and active smokers, and the U.S. Office of the Surgeon General in 2006 said there was insufficient evidence that secondhand smoke causes breast cancer. If the panelists are correct, "they may be offering women a new piece of valuable information with practical advice about how to protect themselves from a common cancer that many fear," according to the Times.

Several experts who were not involved with the panel said any proof that smoking can cause breast cancer is elusive. Michael Thun, a former vice president of epidemiology and surveillance research for the American Cancer Society, said that although it is "definitely plausible" that smoking can cause breast cancer, he "think[s] the jury is still way out." He said, "The issue is, what's the level of the evidence? That's where the disagreement exists" (Rabin, New York Times, 4/24).


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