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Tamoxifen is an oestrogen receptor antagonist which is used in the treatment
of breast cancer
- a partial oestrogen agonist (has antagonistic actions
in breast cancers, but has agonist actions on endometrium, lipids, and bone)
effective at 20 mg/day as at higher doses
- effective in all age groups,
and in premenopausal and postmenopausal women
- beneficial effects greater
when given for five years rather than two - however no evidence shows that tamoxifen
is of additional benefit if taken for more than five years, and it may be detrimental
taken for 5 years following surgical treatment is a standard part of the treatment
regime for postmenopausal women with hormone-receptor-positive breast cancer.
If used in this context then tamoxifen (4)
- increases the proportion of
women who survive for at least 10 years from about 50% to 60% among those with
- increases the proportion of women who survive for
at least 10 years without lymph-node involvement from about 73% to 79%
halves the risk of development of cancer in the contralateral breast
less effective against human epidermal growth factor receptor 2 (HER2) positive
- more effective when given after chemotherapy (when this is also
indicated) rather than concurrently
the International Breast Cancer
Intervention Study (5), which investigated the use of tamoxifen in the unlicensed
indication of breast cancer prevention, revealed that women treated with tamoxifen
had an approximately 2.3x increased risk of venous thromboembolism (VTE) than
those treated with placebo. Approximately 40% of the VTE cases occurred within
3 months of surgery or following immobility. This led to the Chairman of the study,
in March 2002, recommending that women should no longer be treated with tamoxifen
for the PREVENTION of breast cancer (i.e. prevention of occurrence rather than
management of diagnosed disease)
Tamoxifen is also used in the treatment
of anovulatory infertility.
The summary of product characteristics should
be consulted before prescribing this drug.
2006 Jan 28;332(7535):223-4.
- BMJ 2006;332:34-37
- BMJ 2006;332:101-103
- Drug and Therapeutics Bulletin (2003), 41 (8), 57-59.
Problems in Pharmacovigilance (2002), 28, 10.
- BMJ editorial. BMJ 1996;
Last reviewed 03/2021