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The trial that made anastrozole a prevention drug, halving breast cancer in postmenopausal women at high risk and, with a licence granted in 2023, putting a generic tablet on the NHS prevention pathway.
IBIS-II randomised 3,864 postmenopausal women at increased risk of breast cancer to anastrozole or placebo for five years. After a median 131 months, 85 women in the anastrozole arm and 165 in the placebo arm had developed breast cancer, a hazard ratio of 0.51, with the benefit continuing after treatment stopped and no excess of fractures or cardiovascular disease in the post-treatment period. NICE CG164 recommendation 1.7.22, amended in 2023, tells the NHS to offer anastrozole for five years to postmenopausal women at high risk unless they have severe osteoporosis; the MHRA licensed anastrozole for prevention in 2023 through its repurposing programme.
The full inclusion and exclusion criteria are on the registry record. Read 2026-10-07. Recruiting overall does not mean a particular site is open; ask the study team.
Criteria as posted are in the stored snapshot. Read 2026-10-07.
ClinicalTrials.gov data courtesy of the US National Library of Medicine.
Shares Jack Cuzick, Tamoxifen, Breast cancer (all types) and the tags uk, breast, prevention.
Shares Breast cancer (all types) and the tags uk, breast.
Shares Anastrozole, Tamoxifen, Breast cancer (all types).
Shares Breast cancer (all types) and the tags uk, breast.
Shares Anastrozole, Tamoxifen, Breast cancer (all types) and the tag breast.
Shares Breast cancer (all types) and the tags uk, breast.
Shares Breast cancer (all types) and the tags uk, breast.
Shares Anastrozole, Tamoxifen, Breast cancer (all types).
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