Breast cancer drug may cause tumors to spread

Study: Tamoxifen helps cancer cells move when patient is low in a protein

updated 1:54 p.m. ET Dec. 4, 2008

LONDON - The most commonly used breast cancer drug may cause tumors to spread in a small number of women with low levels of a protein which makes cells stick together, British researchers said on Thursday.

The findings could lead to new tests to determine which women are not likely to benefit from tamoxifen and who should be given other drugs, said Stephen Hiscox, a cancer researcher at Cardiff University, who led the study.

"We found something that could be potentially used as a biomarker to determine which kind of drugs they should get because they have low levels of this protein," he said in a telephone interview.