Progress in Blood Test for Breast Cancer

From WebMD Health News

Charlene Laino

April 21, 2010 (Washington, D.C.) — Researchers report they’re a step closer to developing a blood test for the early detection of breast cancer.

Using data from the large Women’s Health Initiative (WHI), they found that levels of epidermal growth factor receptor (EGFR) may be elevated in the blood of women as long as 17 months prior to their breast cancer diagnosis. EGFR is critical for the growth and spread of breast cancer cells.

By itself, EGFR did not prove useful as a marker for breast cancer detection, says Christopher Li, MD, PhD, associate member of the epidemiology program at the Fred Hutchinson Cancer Research Center in Seattle.

The goal is to develop a panel of biomarkers that would be more accurate, he tells WebMD.

EGFR Levels Elevated Before Breast Cancer Diagnosis

The study involved 688 women with estrogen receptor-positive breast cancer whose blood was drawn within 17 months prior to their cancer diagnosis. Their blood test results were compared to those of 688 women of similar ages without any sign of cancer.

The findings were presented at the American Association for Cancer Research 101st Annual Meeting.

Overall, the researchers identified 79 proteins whose levels appeared to be elevated in the blood of women with cancer, compared with the other women.

One of the proteins that could be validated using a commercially available assay was EGFR.

So the researchers divided about 400 of the women into four groups depending on their EGFR levels. Those in the highest quarter had a nearly threefold increased risk of developing breast cancer compared with those in the lowest quarter.

Then the researchers looked only at EGFR levels among the nearly 150 current users of estrogen plus progestin hormone therapy. "We know hormone therapy has a major impact in levels on circulating proteins in the blood," Li explains.

Among these women, those in the highest quarter had nine times the risk of developing breast cancer compared with those in the lowest quarter. Li says the researchers aren't exactly sure why hormone therapy had such a big impact.

As a single marker among current estrogen plus progestin users, EGFR levels could correctly identify 90% of women who would not develop breast cancer.

But they correctly identified only 31% of women who would develop breast cancer.

Panel of Biomarkers Could Be Used for Breast Cancer Screening

Nevertheless, Li is optimistic. "We identified 71 other proteins that may also serve as markers, which we hope to test in the future," he says.

"We also want to see if combining a biomarker panel with mammography will further increase the accuracy of the overall screening approach," Li says.

"This gives us a clue that there may be biomarkers that we can use to better predict breast cancer," says Jennifer Eng-Wong, MD, a breast cancer specialist at Fox Chase Cancer Center in Philadelphia.

Many other studies looking for biomarkers for breast cancer haven’t panned out, the researchers note.

One of the strengths of this study is that the researchers had access to blood drawn prior to women being diagnosed with breast cancer, Eng-Wong tells WebMD.

"If you use blood later, once they’re diagnosed and have clinical symptoms, it's too late," Li says.