Tamoxifen may increase the risk of later tumours being more aggressive

If a woman who takes tamoxifen for breast cancer develops a cancer in her other previously healthy breast, the risk is higher that it will be of a more dangerous type than a contralateral cancer in a woman who has never taken the drug.

Researchers collected data on 8981 women with primary unilateral breast cancer aged at least 50 who had received adjunctive hormonal therapy but not chemotherapy (tamoxifen users) or had received neither hormonal therapy nor chemotherapy (tamoxifen non-users) (Journal of the National Cancer Institute 2001;93:1008-12).

The researchers identified contralateral breast cancers in 89 …