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According to a recent article published in Cancer Causes and Control, long-term smoking can increase a woman’s risk of developing breast cancer by 40%. Furthermore, long-term smoking in addition to mixed hormone replacement therapy (HRT) increases this risk even further.

Breast cancer is diagnosed in over 200,000 women and is responsible for approximately 40,000 deaths annually in the US alone. Due to its prevalence, researchers continue to investigate possible associations between environmental or genetic variables and the development of this disease.

Smoking has been linked to the development of several diseases, including various types of cancer. However, the relationship between smoking and the risk of breast cancer continues to be studied since several different factors may affect its influence on the disease (i.e. duration of time a woman has smoked, average number of pack-years, etc).

Researchers from the Fred Hutchinson Cancer Center in Seattle, Washington, recently conducted a large study to further evaluate a possible association between smoking and the risk of developing breast cancer. This study included nearly 2,000 women aged 65-79 years who lived in the US. Approximately half of the women had been diagnosed with breast cancer; the other half had not.

The following factors gave women a 30%-40% increased risk of developing breast cancer:

  • Current smoking
  • At least an 11 pack-year history of lifetime smoking
  • Starting smoking prior to first full-term birth

Furthermore, women who have taken mixed HRT (estrogen plus progesterone) have an even greater risk of developing breast cancer-over twice that of women who have never smoked or never taken HRT. This increased risk was not seen among HRT containing estrogen only.

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Fortunately, women who quit smoking had their risk of breast cancer decrease; those women who had quit for at least 10 years had a risk equivalent to that of a woman who had never smoked.

Factors such as recent smoking, the intensity of smoking, and the length of smoking were also associated with a modest increase in the development of breast cancer.

The researchers concluded that smoking can greatly increase the risk of developing breast cancer among women aged 65-79 years, particularly those who are currently smokers, have an 11 pack-year or greater history of smoking, or who started smoking prior to their first full-term birth. Furthermore, mixed HRT in addition to smoking increased the risk to over double that of a women who had never smoked or never taken mixed HRT.

Women who smoke may wish to speak with their physician regarding their individual risks of developing breast cancer and about smoking cessation programs.

Reference: Li C, Malone K, Daling J, et al. The Relationship Between Various Measures of Cigarette Smoking and Risk of Breast Cancer Among Older Women 65–79 years of Age (United States). Cancer Causes and Control. 2005; 16: 975-985.

Related News:Initiation of Smoking at Young Age Increases Risk of Breast Cancer

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