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FDA approves blood-based test for colorectal cancer as expert says it could help early detection
Last month the FDA approved the Guardant Shield Blood Collection Kit as an early, noninvasive, and accessible preliminary screening test for colorectal cancer (CRC). It has limited detection accuracy, but some screening is better than no screening, says anatomic pathologist Adam Booth.
The Focus spoke to Adam Booth, MD to get his thoughts on the Guardant Shield Blood Collection Kits FDA approval. He highlighted the tests limitations, including its insensitivity when detecting advanced precancerous lesions, but was broadly positive about the rollout of any kind of test that removes potential barriers [to diagnosis] for some patients.
FDA approves cell-free DNA blood-based test for colorectal cancer screening
The third most diagnosed cancer among adults in the US, colorectal cancer (CRC) kills more than 50,000 Americans every year. Early detection could prevent the lions share of those deaths �up to 90%, in fact.
Research published this year in the New England Journal of Medicine may offer a glimmer of hope to those concerned about the future health of their colorectal systems. The FDA has responded with approval.
In March, researchers published their report on the success of a blood-based test for colorectal cancer. According to their write-up, it had 83% sensitivity for CRC and 90% specificity for advanced neoplasia (meaning: an adenoma 10mm or more in diameter).�
According to a recent news release, the test approved by the FDA has a lower detection rate 55%-65% for Stage I CRC. The agency nevertheless writes that this decision represents the latest example of its ongoing commitment to expanding colorectal cancer screening options for patients.
Anatomic pathologist says detection rate is ‘no subsitute’
Adam Booth, MD told The Focus that a test with a detection rate of 55%-65% is no substitute for a high-quality colonoscopy. Colonoscopies detect colorectal cancer 100% of the time, he says.
However, Booth adds, for some individuals, this may be the only screening method they are comfortable with or able to undergo.
It therefore presents such individuals �and society at large �with an opportunity to catch greater numbers of cases early, and thus prevent symptomatic advanced disease further down the line. Symptoms of CRC often go unnoticed. With any luck, this blood test will go some of the way towards rectifying this issue.
Some screening is better than no screening, Booth stresses. The Guardant Shield Blood Collection Kit test provides at least some CRC screening for individuals uncomfortable with or unable to utilize other modalities.
Without it, CRC cases will continue to go undiagnosed until its too late. The test removes potential barriers for some patients, which is another step forward for US colorectal health.
The test is for people aged 45 and above. However, whatever age you are, if you see blood in your stool, it should ring alarm bells for colorectal cancer. You should seriously consider speaking to a medical professional.
A major concern with the Guardant blood test
Despite overall enthusiasm, Booth notes a major concern with the new screening method.
While it may detect Stage I CRC in a majority of cases, it has very low sensitivity (13%) for detecting advanced precancerous lesions.
These are lesions more than 10mm in size. In stark contrast, a proper colonoscopy can detect precancerous lesions as small as 6mm with a sensitivity of up to 93%, Booth says.
Such lesions can progress quickly, making it important to catch them as early as possible. Whats more, colonoscopy can both diagnose and remove precancerous lesions.
It thereby prevents colon cancer, rather than just screening for it.
Adam Booth is an anatomic and molecular pathologist. He joined the College of American Pathologists in 2023, and is an assistant professor at Washington University School of Medicine in St Louis.
