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Female smokers who develop breast cancer are twice as likely to develop estrogen receptor-negative breast cancer than women who do not smoke, according to the results of a study recently published in the International Journal of Cancer.

Breast cancer is the second leading cause of cancer death in women in the United States, with approximately 200,000 cases diagnosed each year. Although several risk factors have been associated with breast cancer, the cause of the majority of cases of breast cancer remains unknown. Researchers continue to explore the causes and risk factors for this disease in an effort to improve methods for screening and prevention.

Breast cancers are classified as estrogen receptor-positive or estrogen receptor-negative. Estrogen receptor-positive breast cancer is characterized by the overabundance of estrogen receptors to which estrogen binds, facilitating cellular growth and replication. Estrogen receptor-negative breast cancer lacks the presence of these estrogen receptors. Women whose breast cancer is classified as estrogen receptor positive can take anti-estrogens, which block the estrogen receptors, thereby preventing the estrogen-stimulated growth of the breast cancer cells. Women with estrogen receptor-negative breast cancer, unfortunately do not benefit from anti-estrogens.

It has long been known that smoking is associated with a poorer prognosis following a breast cancer diagnosis. Recently, researchers in Sweden conducted a study to evaluate whether smoking was associated with prognostic markers such as hormone receptor status. The researchers evaluated 268 cases of breast cancer from a cohort of 10,902 women who were followed for an average of 12.4 years. Approximately 35% of the women in the study were smokers. The researchers evaluated tumor tissue to assess hormone receptor status.

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The results indicated that both current smokers and ex-smokers had an increased risk of hormone receptor-negative breast cancer. Smokers and ex-smokers were about twice as likely to have estrogen receptor-negative tumors when compared to non-smokers. In addition, ex-smokers had an increased risk of progesterone receptor-negative tumors. The researchers concluded that smoking is associated with an increased incidence of hormone receptor-negative tumors.

More research is needed to define the relationship between smoking and breast cancer; however, the results of this study indicate that women who smoke or have smoked may wish to undergo more frequent screening for breast cancer in order to detect cancer early when it is most treatable. Women concerned with screening for this disease or who may be interested in smoking cessation programs can consult with their physicians for more information. (International Journal of Cancer, Vol. 91, No 3, pp. 580-584, 2001)