Tamoxifen for the Prevention of Breast Cancer in High-Risk Women (IBIS-1)

Inclusion criteria: The entry criteria are based on a relative risk of at least two-fold for women aged 45-70 years, four-fold for women aged 40-44 years and ten-fold for women aged 35-39 years. Age 45-70 years First degree relative who developed breast cancer at age 50 or less First degree relative who developed bilateral breast cancer Two or more first or second degree relatives who developed breast cancer Nulliparous and a first degree relative who developed breast cancer Benign biopsy with proliferative disease and a first degree relative who developed breast cancer Lobular carcinoma in situ Atypical ductal or lobular hyperplasia in a benign lesion 19)Women at high risk who do not fit into the above categories (risk equivalent)* * These women must have clearly apparent family history indicating at least two fold increased risk of breast cancer. Age 40-44 years 8) Two or more first or second degree relatives who developed breast cancer at age 50 or less 9) First degree relative with bilateral breast cancer who developed the first breast cancer at age 50 or less 10) Nulliparous and a first degree relative who developed breast cancer at age 40 or less 11) Benign biopsy with proliferative disease and a first degree relative who developed breast cancer at age 40 or less 12) Lobular carcinoma in situ 13) Atypical ductal or lobular hyperplasia in a benign lesion 14) Women at high risk who do not fit into the above categories (risk equivalent)* * These women must have clearly apparent family history indicating at least four fold increased risk of breast cancer. Age 35-39 years 15) Two or more first degree relatives who developed breast cancer at age 50 or less 16) First degree relative with bilateral breast cancer who developed the first breast cancer at age 40 or less 17) Lobular carcinoma in situ 18) Women at high risk who do not fit into the above categories (risk equivalent)* Exclusion criteria: Pregnant, or at pregnancy risk. If necessary, pre and peri menopausal women must use non-hormonal contraception during the trial. Any previous cancer (except non-melanoma skin cancer or in situ cancer of the cervix). Life expectancy of less than 10 years or other medical condition more serious than the risk of breast cancer. Psychologically and physically unsuitable for five years tamoxifen/placebo therapy. Current treatment with anti-coagulants. Previous deep vein thrombosis or pulmonary embolus. Current tamoxifen use.