First results from the International Breast Cancer Intervention Study (IBIS-1): a randomised prevention trial

Cuzick, J, Forbes, J, Edwards, R, Baum, M, Cawthorn, S, Coates, A, Hamed, H, Howell, A, Powles, T, Clunie, G, Collins, R, Day, N, Northover, J, IBIS investigators and Ward, R (2002) First results from the International Breast Cancer Intervention Study (IBIS-1): a randomised prevention trial. Lancet, 360 9336: 817-824.

Author Cuzick, J
Forbes, J
Edwards, R
Baum, M
Cawthorn, S
Coates, A
Hamed, H
Howell, A
Powles, T
Clunie, G
Collins, R
Day, N
Northover, J
IBIS investigators
Ward, R
Title First results from the International Breast Cancer Intervention Study (IBIS-1): a randomised prevention trial
Journal name Lancet   Check publisher's open access policy
ISSN 0140-6736
Publication date 2002-09-01
Year available 2002
Sub-type Article (original research)
Open Access Status Not yet assessed
Volume 360
Issue 9336
Start page 817
End page 824
Total pages 8
Place of publication London, United Kingdom
Publisher The Lancet Publishing Group
Language eng
Formatted abstract
Background Three clinical trials on the use of tamoxifen to prevent breast cancer have reported mixed results. The overall evidence supports a reduction in the risk of breast cancer, but whether this benefit outweighs the risks and side-effects associated with tamoxifen is unclear. Methods We undertook a double-blind placebo-controlled randomised trial of tamoxifen, 20 mg/day for 5 years, in 7152 women aged 35-70 years, who were at increased risk of breast cancer. The primary outcome measure was the frequency of breast cancer (including ductal carcinoma in situ). Analyses were by intention to treat after exclusion of 13 women found to have breast cancer at baseline mammography. Findings After median follow-up of 50 months (IQR 32-67), 69 breast cancers had been diagnosed in 3578 women in the tamoxifen group and 101 in 3566 in the placebo group (risk reduction 32% [95% CI 8-50]; p=0•013). Age, degree of risk, and use of hormone-replacement therapy did not affect the reduction. Endometrial cancer was nonsignificantly increased (11 vs 5; p=0•2) and thromboembolic events were significantly increased with tamoxifen (43 vs 17; odds ratio 2•5 [1•5-4•4], p=0•001), particularly after surgery. There was a significant excess of deaths from all causes in the tamoxifen group (25 vs 11, p=0•028). Interpretation Prophylactic tamoxifen reduces the risk of breast cancer by about a third. Temporary cessation of tamoxifen should be considered and the use of appropriate antithrombotic measures is recommended during and after major surgery or periods of immobilisation. Prophylactic use of tamoxifen is contraindicated in women at high risk of thromboembolic disease. The combined evidence indicates that mortality from non-breast-cancer causes is not increased by tamoxifen. The overall risk to benefit ratio for the use of tamoxifen in prevention is still unclear, and continued follow-up of the current trials is essential.
Keyword Postmenopausal Women
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Office of the Vice-Chancellor
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