Marker protein may help breast cancer screening

WASHINGTON — High concentrations of a protein implicated in several cancers may be an early warning sign of undiagnosed breast cancer, a new study suggests. Blood samples taken months before breast cancer was diagnosed show the receptor was elevated more often in women with the disease than in women who didn’t develop breast cancer, scientists reported April 20 at a meeting of the American Association for Cancer Research.

Although the marker isn’t a sure indication of incipient breast cancer, it might eventually contribute to that diagnosis, said study coauthor Christopher Li, a physician and epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle who presented the findings. “There is considerable investment in trying to discover this disease while it is most treatable,” he said.

Li and his colleagues analyzed blood samples obtained from 688 women who had developed breast cancer while participating in a large medical trial and from 688 others in the trial who hadn’t developed cancer. The two groups were matched for race, ethnicity and age.

The blood samples had been drawn from the cancer patients up to 17 months before their diagnosis. The researchers focused on EGFR, or epidermal growth factor receptor, a cell-surface receptor protein that can trigger pro-growth behavior in a cell, such as proliferation, survival and migration.

Women with the highest levels of EGFR were nearly three times as likely to develop breast cancer as were women with the lowest levels. Among women who were taking estrogen and progesterone for menopausal hormone therapy at the time their blood was drawn, those with the highest EGFR levels were nine times as likely to develop breast cancer compared to women with the lowest EGFR levels.

Previous work has linked elevated EGFR to cancers. For that reason, EGFR testing is already ordered sometimes for people who have been diagnosed with cancer of the breast, lung, colon, pancreas and other tissues. In those cases it can help doctors decide whether to prescribe specific drugs based on antibodies to EGFR.

This work shows that subtle changes in the protein population in the blood may indicate the presence or heightened risk of otherwise hidden tumors, Li said. But the test for elevated EGFR only modestly distinguishes between people with breast cancer and those without it. “We don’t believe EGFR will be a stand-alone marker. Our goal would be to compile a panel of such markers,” Li said.

Screening healthy people for high EGFR levels isn’t current practice, said David Solit, a medical oncologist at Memorial Sloan-Kettering Cancer Center in New York City. Using biomarkers as predictors of cancer remains a possibility, but the science needs to be further refined, he said. As more biomarkers show value, doctors might check them in high-risk populations, such as women with a family history of breast cancer. High EGFR, in combination with other predictors, might push a doctor to look harder, order a biopsy or repeat biomarker tests at regular intervals to see if the scores change. Meanwhile, Solit said, “as a diagnostic, this is in a very early stage.”