An international multi-centre study of tamoxifen vs placebo in women at increased risk of breast cancer.

INTERVENTION: Arm A: Tamoxifen 20 mg/day tablet orally for 5 years CONDITION: Prevention of Breast cancer PRIMARY OUTCOME: All cause and cause‐specific mortality. Breast cancer mortality. Development of histologically confirmed breast cancer (both invasive and non‐invasive i.e. including Ductal Carcinoma Insitu (DCIS)). SECONDARY OUTCOME: Occurrence of and mortality from myocardial infarction. INCLUSION CRITERIA: Women must satisfy at least one of the entry criteria listed below. A) Age 45‐70 with at least one of the following: 1. Breast cancer in mother, sister or daughter diagnosed under the age of 50 2. Mother, sister or daughter with cancer in both breasts at any age 3. Any two first or second degree relatives (blood relatives) with breast cancer 4. Having no children, and with a mother or sister with breast cancer at any age 5. Having had a benign biopsy with proliferative disase and a mother, sister or daughter who developed breast cancer at any age 6. Having had a biopsy with lobular carcinoma in situ 7. Having had a benign biopsy with atypical ductal or lobular hyperplasia 8. "Other" equivalent risk to the above (to be confirmed by the Study Chairman B) Age 40‐44 with at least one of the following: 9. Any two first or second degree relatives (blood relatives) with breast cancer under the age of 50 10. Mother, sis