[Smoking and breast cancer].

Two hypotheses have been suggested concerning the relationship between smoking and breast cancer: 1) smoking has a protective effect on the development of breast cancer because of an anti-oestrogenic effect; 2) smoking increases the risk of breast cancer because of a direct carcinogenic effect. The present study examined the relationship between smoking and breast cancer in 3240 women who were referred for mammography. There was no support for the first hypothesis. In contrast, women had an increased risk of developing breast cancer after 30 years of smoking with a relative risk of 1.6, and smokers with breast cancer were eight years younger than non-smokers with breast cancer.