Tamoxifen is a drug credited with saving the lives of hundreds of thousands of women around the world, and extending the lives of millions more. Listed by the World Health Organisation as an essential drug for the treatment of breast cancer, Tamoxifen has been a critical weapon in the fight against this disease for more than 35 years.
First made in 1966, Tamoxifen was intended as a new contraceptive drug, before scientists realised that it could be useful for treating breast cancer. In 1977 it was approved for use in patients with advanced breast cancer, and during the 1970s and 80s, a number of clinical trials showed it to be safe and effective for the treatment of breast cancer more broadly.
Tamoxifen has become the gold standard treatment for women with a type of breast cancer called ‘oestrogen receptor positive’ (or ER positive), which account for about 8 out of every 10 breast cancers diagnosed. These cancers grow in response to the hormone oestrogen, and so are responsive to drugs like Tamoxifen that act to block oestrogen from entering cancer cells.
Tamoxifen offers an important advantage over chemotherapy drugs by specifically targeting cancer cells, and leaving normal cells unharmed. As a result, it causes far fewer and less serious side-effects.
Recently, clinical trials have been investigating the potential benefits of giving Tamoxifen to women who are at high risk of breast cancer. This approach, called chemoprevention, may make it possible to prevent some women from ever getting breast cancer, simply by taking this drug.