FRIDAY, Dec. 28 (HealthDay News) For breast cancer patients
prescribed tamoxifen to treat their disease, genetic traits
affecting an enzyme in the liver are major players in determining
the impact of the hormone therapy, new research suggests.
There's been debate in the scientific world for years over the
role of genetic differences in the enzyme, known as CYP2D6. An
estimated 5 percent to 7 percent of European and North American
women have a trait that prevents the enzyme from working
"Our findings confirm that, in early breast cancer treated with tamoxifen, genetic alterations in CYP2D6 lead to a higher likelihood of recurrence and death," Dr. Matthew Goetz, a Mayo Clinic oncologist and lead author of the study that reported the findings, said in a Mayo Clinic news release.
The researchers tracked two groups of women: postmenopausal
women with primary estrogen receptor-positive breast cancer who
received tamoxifen for five years, and those took got the drug for
two years followed by another drug, anastrozole, for three
Among those who took tamoxifen for five years, those whose
genetic makeup prevented the enzyme from being able to process
things were 2.5 times more likely to die or have their cancer
return than those whose enzymes worked normally, the investigators
However, genetic traits involving the enzyme didn't seem to
influence the fates of the women who switched to anastrozole, an
aromatase inhibitor, after two years of tamoxifen, the study
"Switching from tamoxifen to an aromatase inhibitor may be one reason for the discrepant studies surrounding CYP2D6 and tamoxifen -- as information about whether a patient took an aromatase inhibitor after tamoxifen was not available in most of the prior studies," senior author Dr. James Ingle, of the Mayo Clinic, said in the news release.
Goezt thinks the study findings confirm that women should switch
from tamoxifen to an aromatase inhibitor, or avoid tamoxifen
altogether, if tests show they have the genetic trait that limits
the metabolizing process.
The study was released online in advance of publication in an
upcoming print issue of the journal
Clinical Cancer Research.
For more about
breast cancer, visit the U.S. National Library of Medicine.