Gene Predicts Tamoxifen Success in Breast Cancer
Study Shows Women With a Gene Variant Respond Better to Tamoxifen Treatment
Oct. 8, 2009 -- A single gene variant predicts breast cancer survival after tamoxifen treatment, a new study finds.
In the 46% of women with the "good" gene, tamoxifen works as well as newer
drugs. For women with the gene variant linked to poor
response to tamoxifen treatment, other treatment strategies would be a better
In the past 25 years, tamoxifen has prevented more than half a
million deaths from breast cancer. The drug helps prevent breast cancer recurrence
after surgery. Tamoxifen is still a useful drug, although newer drugs called
aromatase inhibitors seem to work better in clinical trials.
Now it appears that some women will do at least as well if they're treated
with tamoxifen. Such women carry a version of a gene called CYP2D6 that
makes tamoxifen work better.
The gene encodes an enzyme crucial to tamoxifen activity. About 46% of women
have a version of the gene that contributes to high enzyme activity. Others
have genes that contribute to low or intermediate activity of the enzyme.
Werner Schroth, PhD, of Germany's Fischer-Bosch Institute of Clinical
Pharmacology, and colleagues analyzed CYP2D6 genes in 1,325
postmenopausal women treated with tamoxifen for early-stage breast cancer in
Germany and in the U.S.
They found that women with the highly active version of the gene were
significantly less likely to have their breast cancer come back after five
years of tamoxifen treatment. These women had outcomes similar to those seen in
women treated with aromatase inhibitors.
"[This] should provide new impetus to the medical and scientific community
to revisit the issue of the relative efficacy of these two approaches in women
with early breast cancer," Schroth and colleagues conclude.
The researchers suggest that genetic testing could identify women who should
not be treated with tamoxifen.
Schroth and colleagues report the findings in the Oct. 7 issue of
TheJournal of the American Medical Association.