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Smoking Increases Breast Cancer Risk Based on Genetic Trait

Posted Mar 03 2010 7:35am
Smoking is thought by many people to be a risk factor for breast cancer.  However, the specific mechanisms by which smoking might increase breast cancer risk remains an area of intense investigation.  One potential mediator of tobacco use on breast cancer risk is an enzyme called N-acetyltransferase 2 (NAT2).  This enzyme is a metabolic enzyme known to convert some chemicals and drugs into cancer causing agents in some individuals.   The rates of these conversions are classified as slow or fast acetylators.  Recently published breast cancer research has explored this relationship between smoking, NAT2, and breast cancer risk.

In this new study , investigators conducted a population-based study that included nearly 350 women diagnosed with breast cancer and 775 control women without breast cancer.  Study volunteers answered questionnaires about smoking habits and other breast cancer risk factors and an analysis was done to determine their NAT2 status.  The results of this study showed that
  • Never-active smokers exposed to second-hand smoke over a long period of time had about an 86% increased risk for breast cancer.
  • This increased breast cancer risk to second-hand smoke was greater in slow acetylators, but not increased for fast acetylators.
  • Active smokers showed about a 34% increase in breast cancer risk.
  • Among active smokers, breast cancer risk was further increased among study volunteers classified as NAT2 fast acetylators (~93% risk for breast cancer), but not among NAT2 slow acetylators.
  • Women who were both fast acetylators and had been active smokers for the longest period of time were at more than a 200% risk for breast cancer.
These are interesting and important results that help to more clearly understand the potential impact of smoking, both active and passive, on breast cancer risk.  Overall, these results suggest that not only does both active and passing smoking increase breast cancer risk, but that individual differences in the NAT2 metabolic enzyme modifies each person's breast cancer risk.  The link between breast cancer risk and tobacco use is controversial .  Some studies suggest an increased breast cancer risk with smoking, while other studies report no link between smoking and breast cancer risk.  While this new study does not completely clear up this controversy, it does provide evidence that the possible link between smoking and breast cancer risk might be dependent upon individual genetic factors.  Considering the other known adverse health effects of smoking and the possible link to breast cancer, reducing tobacco smoke exposure might be one lifestyle change that can help us all lead a healthier lifestyle.

To learn more about other diet and lifestyle changes that you can make to reduce your risk of breast cancer, read my book Fight Now: Eat & Live Proactively Against Breast Cancer at
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