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  • Writer's pictureNick Allen

Liquid biopsies: the future of early cancer detection?

I was reviewing a patient’s chart this week and was surprised to see a result for a test I had never heard of. “Galleri test negative” was all that was said. A quick search led me to the website for Galleri, a “multi-cancer early detection test” from California-based biotech company GRAIL. The concept of a liquid biopsy, or a blood test to detect cancer very early in its course, is not that new. I was well aware that companies were working on products like this, and I’ve been excited about the potential of these tests for years. Nevertheless, I was quite surprised to see one of them being used in mainstream clinical practice.

This technology is still in its infancy, and the patient who got this test had to pay for the full $949 completely out-of-pocket. This is because the test isn’t yet FDA approved (this will likely come in the next year or two), and therefore isn’t covered by insurance. The test’s performance is encouraging, however, and the science behind it is solid. In simple terms, when a cancer is present, some of the cancerous cells will die and release DNA into the bloodstream. Tests like Galleri are designed to detect this circulating tumor DNA and even identify the likely origin of the cancer. Once an organ is identified as the potential source, that organ can be imaged or otherwise tested using existing technology to confirm the diagnosis.

Experts in this area have been clear that liquid biopsies are not meant to replace current cancer screenings like colonoscopy, pap smear, mammography, and more. Instead, utilizing both approaches in combination can potentially provide two key benefits. Firstly, for the tests where screening is already available, detection may come earlier with a test like Galleri. Secondly, you can screen for far more cancers using a liquid biopsy than with any traditional screening methods. Many cancers have no screening test currently available, and thus by the time the cancer is discovered it’s generally too late for effective treatment. Galleri and other liquid biopsies could change that.

With all the promise this technology brings, I think it’s important to note that this is a great example of the stratification we see in healthcare. For a patient like the one I saw in clinic to get this test in 2023, they have to firstly be aware that it exists. This educational barrier is exactly what we’re hoping to erode with this post and others on the blog. The second criteria, however, is that they have to be able to afford the $949 price tag. Until tests like this are covered by insurance or otherwise made significantly cheaper, they’re basically off-limits to low-income populations. So while we’re excited for the future of Galleri and other liquid biopsies, these tests still have many hurdles to overcome.


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