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Wolfson Institute of Preventive Medicine - Barts and The London


Centre for Cancer Prevention

Funding Body:  Cancer Research UK

Principal Investigator:  Professor Jack Cuzick


The International Breast Cancer Intervention Study 1 (BISI-1) was designed to investigate the use of tamoxifen in preventing breast cancer in women with a higher risk of developing the disease.  Recruitment of women to IBIS-1 ended in March 2011 and it recruited 7,154 women from 36 centres in 9 countries.

A trial of tamoxifen (20mg/d for 5 years) versus placebo in 7,154 women at high risk of breast cancer.  The 10 year results show a 27% reduction in new breast cancers.  The long-term follow up and 20 year results were presented in December 2014 at the San Antonia Breast Cancer Symposium.  The trial was also used to study the impact of tamoxifen on breast density, with first evidence that the response to endocrine therapy is predictable by 12-18% reductions in breast density.


Cuzick J, Sestak I, Cawthorn S, Hamed H, Holli K, Howell A, Forbes JF ; IBIS-1 Investigators (2015). Tamoxifen for prevention of breast cancer: extended long-term follow-up of the IBIS-I breast cancer prevention trial. Lancet Oncol, 16(1):67-75.

Cuzick J, Forbes JF, Sestak I, Cawthorn S, Hamed H; Holli K, Howell A (2007). Long-Term Results of Tamoxifen Prophylaxis for Breast Cancer – 96-Month Follow-up of the Randomized IBIS-I Trial. JNCI99: 272-282.

Cuzick J, Warwick J, Pinney E, Warren RML, Duffy SW (2004). Tamoxifen and breast density in women at increased risk of breast cancer. J Natl Cancer Inst, 96: 621-628.

Cuzick J, Forbes J, Edwards R, Baum M, Cawthorn S, Coates A, Hamed A, Howell A, Powles T; IBIS Investigators (2002). First results from the International Breast Cancer Intervention Study (IBIS-I): a randomised prevention trial. Lancet, 360: 817-24.