[Is breast cancer prevention by tamoxifen possible?].

Breast cancer is a frequent disease especially in the Western world with an incidence that increases by 1% each year. Distressingly, even nowadays, 40% of patients with breast cancer will die of their disease. Postoperative adjuvant therapy and detection of non-palpable cancers by mass screening of women have improved patient survival but have not impinged upon the steady increase in incidence. Treatment before radiological detection could improve the chances of survival and even prevent the full-blown expression of the disease. The probability that a woman will develop breast cancer during her life-time is high but not evenly distributed. Knowledge of predisposing factors can help to identify those women subject to greater risk than the general population. The most important known risk factors are age, family history, factors related to ob-gyn antecedents, lifestyle, benign hyperplastic breast disease with or without atypia. These various risks, are often associated and cumulative. A woman who has already had breast cancer has a 3 to 5 times greater probability of developing cancer of the contralateral breast than the average woman. The second breast is therefore at risk in the same way as are the women with predisposing factors. Many clinical studies have demonstrated the benefits of postoperative adjuvant tamoxifen (TAM) in improving the disease-free interval and survival of patients. An analysis of the site of relapse has interestingly brought to light a marked decrease in the percentage of cancers of the contralateral breast. In order to establish whether TAM could prevent or delay the onset of high-risk women without detectable signs of illness into groups receiving either TAM or placebo. Is this ethically acceptable? The answer to this question rests heavily on an objective evaluation of the unwanted and beneficial side-effects of TAM in order to weigh up all pros and cons before initiating a trial.