Women diagnosed with estrogen-positive breast cancers are frequently prescribed the anti-estrogen drug tamoxifen as a follow-up treatment. This medication and its metabolites bind to estrogen receptors in the breast so that natural estrogen cannot stimulate breast tissue. Over the five years of recommended treatment, tamoxifen is associated with a lower risk of recurrences, fewer new cancers and improved survival.
But a new study suggests that tamoxifen is not free of complications. Scientists at the University of Washington reviewed medical histories of more than 1000 women. Those taking tamoxifen quadrupled their risk of a rare type of breast tumor. These cancers are not sensitive to estrogen so they are harder to treat. This new finding has created considerable controversy and confusion. The investigators emphasize that women taking tamoxifen should not stop, since the drug clearly has valuable benefits. But this new study suggests that sometimes there may be hidden risks that don’t reveal themselves for years.
[Cancer Research, Aug. 25, 2009]
