Gene May Undermine Tamoxifen's Effectiveness

A common gene mutation may render the cancer-preventing drug tamoxifen less effective in preventing tumor recurrence in some breast cancer survivors, a new study suggests. This genetic change in the CYP2D6 gene lowers levels of an important liver enzyme called Cytochrome P4502D6, which is responsible for tamoxifen metabolism, according to researchers at the Mayo Clinic and the University of Michigan. Up to 10 percent of white patients may have this genetic change and these women are nearly twice as likely as other women to suffer a cancer relapse while receiving tamoxifen, the study found. The findings appear in the Dec. 20 issue of the Journal of Clinical Oncology.