A not-so-new tumor-cell biomarker has been newly unveiled by researchers. And it just might predict how well women will fare after they've been diagnosed with breast cancer and how to best treat each cancer.

When expression of the marker -- called p27 -- is low, especially among women with hormone-receptor-positive tumors, prognosis is typically poor.

P27 was first discovered more than a decade ago but has not been useful for prognostic purposes until now. Previous studies on the marker failed to deliver all patients the same treatment -- so researchers could never determine if outcomes were due to p27 or treatment. But a recent study -- published in the December 6 issue of the Journal of the National Cancer Institute -- followed the same patients receiving the same treatment for newly diagnosed, hormone-receptor-positive, moderate-risk breast cancer.

The new study found women with tumors high in p27 expression had a five-year survival rate of 91 percent. Women with a low expression had a five-year survival rate of 85 percent.

No association was found between p27 expression and survival among women with hormone-receptor-negative tumors.

The next step in the study of this potentially important marker is to better define how women will benefit from this information.