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NEW YORK — For people with cancer or suspected cancer, the biopsy is a necessary evil — an uncomfortable and somewhat risky procedure to extract tissue for diagnosis or analysis.

Lynn Lewis, a breast cancer patient in Brooklyn, has had her cancer analyzed an easier way: simple blood tests that are being called “liquid biopsies.”

Telltale traces of a tumor are often present in the blood. These traces — either intact cancer cells or fragments of tumor DNA — are present in minuscule amounts.

But numerous companies are now coming to market with sophisticated tests that can detect and analyze them.


While the usefulness of the tests still needs to be proved, proponents say that because liquid biopsies are not invasive, they can be easier to repeat periodically, potentially tracking the disease as it evolves and allowing treatments to be adjusted accordingly.

“Being able to do it serially is a huge advantage,” said Dr. Pamela Munster, an oncologist at the University of California San Francisco. “We can’t serially biopsy a patient’s liver.”

Early warning could be one use. A study published in The New England Journal of Medicine, for instance, showed that in some cases a liquid biopsy could detect the worsening of breast cancer five months before it could be seen by CT scans.

That could allow an ineffective therapy to be abandoned earlier.

For all of the potential of liquid biopsies, however, the developers of such tests for the most part have not yet established their accuracy and, more important, their usefulness.

Lewis, 54, who has been battling metastatic breast cancer for seven years, is a case in point.

In June, she had a test of tumor DNA fragments in her blood developed by a startup called Guardant Health.

It found a genetic mutation that suggested her disease would be susceptible to the drug Afinitor. Lewis, however, had previously tried Afinitor and it had stopped working.


A different liquid biopsy found that at least some of Lewis’s cancer cells had abundant amounts of the protein Her2, which drives tumor growth. That had not been seen on her tissue biopsies, perhaps because such biopsies sample only a tiny bit of what is typically a heterogeneous tumor.

As a result, Lewis has just started on Herceptin and Tykerb, two drugs for Her2-positive cancers.

“You will have a chance to identify a treatment sometimes, and sometimes not,” said Dr. Massimo Cristofanilli, director of the breast care center at Thomas Jefferson University in Philadelphia, who is treating Lewis and is a leading expert on liquid biopsies. Still, he said, “you are certainly much more advanced than going blindly.”