Dr. C. Kent Osborne, director of the Breast Center at Baylor College of Medicine in Houston, and his collaborators found that when a protein called AIB1 (Amplified in Breast Cancer-1) as well as another called HER-2 is present in high levels in the cells of women who have had breast cancer, their tumors are resistant to the cancer-fighting effects of tamoxifen.
"In fact, tamoxifen might have an adverse effect," said Osborne. The finding could be important in predicting which women will respond to tamoxifen therapy. Before the finding can be used in patient treatment, it must be confirmed in studies with more patients, he said.
He and his colleagues determined the AIB1 and HER-2 levels in the tumors of 316 breast cancer patients. They then correlated these levels with how long the women lived without recurrence of their disease.
They found that women with high levels of AIB1 and HER-2 had worse outcomes with tamoxifen therapy than all other women combined, Osborne said.
When the level of either protein is low, then the tamoxifen problem does not occur, he said.
His coauthors include Drs. Valerie Bardou, Torsten A. Hopp, Gary C. Chamness, Susan G. Hilsenbeck, Suzanne A.W. Fuqua, Jiemin Wong, D. Craig Allred, Gary M. Clark and Rachel Schiff, all of Baylor.
Journal
JNCI Journal of the National Cancer Institute