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Traditionally, doctors have used surgery to perform tissue biopsies to detect cancer, assess its characteristics, and determine the best treatment options. While surgical biopsies are critical to appropriate cancer treatment, they are invasive, painful, and come with the risks of any surgery. Sometimes, doctors cannot perform the biopsies needed because the patient isn’t well enough for surgery or the tumor is in a difficult place in the body to reach safely.
But all of that may be changing. Less than a year ago, the Food and Drug Administration (FDA) approved the first liquid biopsy to detect cancer, a minimally invasive blood test. This first approval was specific to advanced non-small cell lung cancer. But more cancer blood tests are becoming available as a large volume of research shows they can be used effectively to detect and treat advanced breast cancer, melanomas, and other cancers.
Whether a blood test is the right choice for cancer screening depends upon many factors, including the type and stage of cancer. Always talk with your doctor about your options and ask questions about the risks and benefits of each one.
How Liquid Biopsies Work
Liquid biopsies test a blood sample for the presence of cancer DNA. Cancer tumors shed two types of DNA into the bloodstream:
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Circulating tumor cells (CTCs)
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Cell-free circulating tumor DNA (ctDNA)
CTC cancer blood tests give doctors invaluable information about the stage and spread of cancer. They can also indicate specific gene mutations that may best respond to innovative targeted therapy. CTC tests can also be used to monitor the effectiveness of treatment. If the cancer is resistant to treatment, the tests can indicate the reasons why. After treatment, CTC tests can be used in follow-up to catch early warning signs of cancer recurrence.
ctDNA is a next-generation cancer blood test with the ability to detect tumor changes as they happen at the molecular level. This gives doctors the ability to monitor the changes for a more specific picture of cancer development and treatment resistance.
The Effectiveness of Liquid Biopsies vs. Traditional Biopsies
Research has shown liquid biopsies to be almost as effective as traditional tissue biopsies for certain types and stages of cancer, particularly cancer in advanced stages.
In a recent study comparing the effectiveness of a ctDNA blood test with a traditional tissue biopsy in detecting cancer, the ctDNA blood test was successful in detecting cancer in 82% of people with solid tumors outside the brain. The test was successful in detecting cancer in 75% of people with advanced breast, ovarian, colorectal, and pancreatic cancers.
In another study, a ctDNA blood test detected 94 to 99% of the cancerous gene mutations detected in biopsy tissue. The genes included:
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BRAF, melanoma
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EGFR, non-small cell lung cancer
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KRAS, non-small cell lung cancer
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PIK3CA, colorectal cancer
The same study showed that, overall, the liquid biopsy performed with 87% of the accuracy of tissue biopsy. The accuracy was higher, at 98%, for blood tests and tissue biopsies performed within six months of each other. What’s more, in 27% of the cases, the cancer blood tests uncovered indicators of resistance to certain targeted treatment options that tissue biopsies did not reflect.
What’s Next in Liquid Biopsies
Blood tests for cancer are not yet routine, but many physicians believe they will become a new standard of care in the coming years. Researchers also anticipate that as today’s cancer blood tests are refined, they will accurately detect cancer at earlier stages, including the pre-cancerous stage. Innovations are happening rapidly, so stay informed, and ask your doctor about the latest cancer screening options available to you.