Breast Proteins Curb Tamoxifen's Effect

Cancer-fighting drug affected by high levels of 2 proteins

TUESDAY, March 4, 2003 (HealthDayNews) -- High levels of two proteins that affect the growth of breast cancer cells curb the effectiveness of the anti-cancer drug tamoxifen.

Researchers from the Baylor College of Medicine found that when there are high levels of the proteins AIB1 and HER-2 in the cells of women who have breast cancer, their tumors are resistant to tamoxifen's cancer-fighting effects and the drug might actually have an adverse effect.

Their research appears in the March 5 issue of the Journal of the National Cancer Institute.

Tamoxifen is used to to fight new breast cancers and prevent recurrences of the disease in women at risk.

The study's finding could provide important information about predicting which women will respond to tamoxifen therapy. However, studies with more patients are needed to confirm the finding.

The Baylor study included 316 breast cancer patients. The researchers determined the AIB1 and HER-2 levels in the women's tumors and then correlated those levels with how long the women went without recurrence of breast cancer.

Women with high levels of the two proteins had worse outcomes with tamoxifen therapy than all other women combined. In women with low levels of either protein, there was no problem with the tamoxifen therapy.

More information

The U.S. National Cancer Institute has more information about tamoxifen.

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