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- Doctors typically gather information about tumors via biopsies.
- Some tumors are not easily sampled.
- Liquid biopsies based on blood samples could fill those gaps.
When a patient potentially has a cancer diagnosis, doctors typically need to order a biopsy, which can involve an invasive surgery and in some cases are not possible. With new liquid biopsies based on blood samples entering the market, they have more options for early diagnosis that are less invasive and which could potentially help make treatment more effective.
Two tests were recently approved by the U.S. Food and Drug Administration (FDA): a test from Guardant Health and another test from Foundation Medicine. Both are looking for signs of non-small cell lung cancer and solid tumors. Guardant Health’s test, called Guardant360 CDx, is approved for profiling for all kinds of solid cancers and works by looking for mutated cancer cell DNA that’s circulating in the body. Foundation Medicine’s test, called FoundationOne Liquid CDx, looks for about 300 genes in a blood sample.
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The tests can be used to manage the care of cancer patients because the tests give a real-time assessment of the state of the disease, especially if they are continually testing the patient. According to the FDA profile, Guardant360 CDx is meant to be paired with the treatment osimertinib. FoundationOne Liquid CDx can be paired with a few treatments including osimertinib, rucaparib and erlotinib, according to the FDA profile.
Although sampling from a tumor itself is more direct, liquid biopsies can provide useful information early on and during the treatment course itself. Liquid biopsies can be done more cheaply and easily than tissue biopsies, which means they can be performed more frequently as well. Physicians can use the liquid biopsy results to monitor how a treatment is progressing and decide whether they need to change strategy.
“I think that liquid biopsies now are coming into their own," says Matthew Freedman, who is an oncologist and researcher at the Dana-Farber Cancer Institute in Boston, to USA Today.
Studies suggest that liquid biopsies can detect a range of cancer types at different stages. For example, one study found that the tests could detect more than 50 types and across all four stages of cancer.
That doesn’t mean that liquid biopsies are better or can do the job of a regular biopsy. Since tumor biopsy at the time of cancer diagnosis gives important information directly from the tumor, “it is unlikely that tumor biopsy will be ‘replaced’ by liquid biopsy,” writes Ryan B. Corcoran in Nature Medicine.
But liquid biopsies used as a companion tool can be valuable. The evidence suggests that liquid biopsy can be used reliably to match patients to clinical trials, writes Corcoran. And that could be crucial in the fight against cancer.
Physician Toni Choueiri says to USA Today, “You want to cure cancer. You don't cure it with third-line chemo. You want to cure it before it happens.”
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