SPORE Study Provides New Guidelines for Tamoxifen Use
Approximately half a million women in the United States alone
currently take the drug tamoxifen, either as an adjuvant therapy
for preinvasive or invasive breast cancer, or as a
chemopreventive agent for those at high risk of the disease.
Now, a new study led by Dr. Matthew Goetz, an investigator for
the Breast Cancer Specialized Program of Research Excellence
(SPORE) at the Mayo Clinic, has shown that up to 10 percent of
women taking the drug may not receive the intended benefit due
to genetic differences in the way tamoxifen is metabolized.
Additionally, a larger percentage of women may be at increased
risk of treatment failure because of drug interactions. Both
genetic polymorphisms and many commonly administered drugs -
such as selective serotonin reuptake inhibitors - can affect the
activity of an enzyme called cytochrome (CYP) 2D6. Dr. David
Flockhart's group, which is funded by the National Institute of
General Medical Science's Pharmacogenetics Res