Researchers designed a liquid biopsy test to determine a patient’s risk of colon cancer recurrence and monitor the effects of chemotherapy after surgery.
Earlier this month, a team of researchers from Johns Hopkins University and the Walter and Eliza Hall Institute of Medical Research in Australia published a study suggesting that they could pretty accurately predict if a colon cancer patient would have a recurrence of the disease. After doing a series of liquid biopsies on 230 patients over two years, they found that 79 percent of the patients whose blood still had traces of tumor DNA after surgery suffered a relapse. These were all patients with stage 2 colon cancer that had not yet metastasized.
The test wasn’t perfect. Almost 10 percent of the patients who didn’t appear to have tumor DNA in their blood had their cancers come back. Still, the scientists said the liquid biopsies could provide a strong indication as to whether a patient was cured through surgery or if he or she also needed to be treated with chemotherapy to take care of cancer traces that remained.
Last month, at the American Society of Clinical Oncology conference in Chicago, researchers presented the largest study yet of liquid biopsies, reporting that blood tests to detect cancer mutations largely agreed with what was found through conventional biopsies. In that case, the scientists analyzed more than 15,000 liquid biopsies that had been performed by Guardant Health, a Silicon Valley startup.
Those impressive results were for a gene mutation associated with tumor growth. There was less agreement between the two types of biopsies, however, when the scientists analyzed mutations that indicate potential resistance to certain drugs. Also, for about 15 percent of the patients overall, the liquid biopsies didn’t show any evidence of the tumor.
But there is a Reality Check:
This recent research does boost the prospects for liquid biopsies, but the tests still have a long way to go before they’re considered reliable enough to replace more invasive biopsies. So far, studies have involved samples from patients who were already known to have cancer. That suggests liquid biopsies could be useful in monitoring tumors to determine if a treatment has been effective.
But the evidence is less convincing that they can be trusted to find cancer on their own. Medical professionals worry about false negatives, in cases where some cancers may not secrete the DNA fragments early in the development of the disease, and false positives, where a test may pick up evidence of cancer in a very early stage that could be eliminated by the body’s immune system. Those patients might end up going through an unnecessary round of invasive tests. The overall concern is that patients may begin viewing liquid biopsies as a relatively painless screening test for all cancers, and will start requesting them to avoid unpleasant procedures, such as colonoscopies.
“I would argue that implementing an unproven screening program could violate the medical affirmation to ‘first, do no harm,'” wrote Richard Hoffman in the Health News Review. Hoffman, director of the Division of General Internal Medicine at the University of Iowa Carver College of Medicine, argues that more evidence is also needed to show that early detection will actually increase a patient’s lifespan, so that they’re not submitted to the physical and financial demands of treatment years before it’s necessary.