Tamoxifen Speeds Diagnosis of ER-Negative Breast Cancer

A treatment that helps prevent one type of breast cancer in women with an evaluated risk of the disease also appears to help doctors make an earlier diagnosis of another form of breast cancer, a new study reports.

Tamoxifen previously had been shown to reduce the risk of estrogen receptor (ER) positive breast cancer in women at high risk of the disease, but not to affect the chance of developing ER-negative disease.

However, the study by researchers at the University of Texas M.D. Anderson Cancer Center in Houston found that the treatment helped doctors diagnosis women who later developed estrogen receptor (ER) negative breast cancer an average of one year sooner than the same at-risk patients who instead took a placebo.

For the study, 13,388 women at high risk of breast cancer participated in the trial; 174 women were diagnosed with ER-positive tumors and 69 women with ER-negative tumors. The median time to diagnosis for ER-negative disease was 36 months in the placebo group but only 24 months in the tamoxifen group.

The median time to diagnosis for ER-positive disease was similar in the placebo and tamoxifen groups at 43 and 51 months, respectively, which is not statistically different.

It's not clear why the diagnosis time of ER-negative tumors is so different, but the authors hypothesized that the drug may make the tumors more detectable. No evidence was found that tamoxifen altered the growth rate of ER-negative disease.

The study was published online Oct. 7 in the Journal of the National Cancer Institute.

The findings should be investigated further, the researchers concluded.

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