On Monday, the Food and Drug Administration approved Guardant Health’s blood test, called Shield, to screen for colon cancer. The test isn’t meant to replace colonoscopies but is generating enthusiasm among doctors who say it has the potential to boost the dismal rate of screenings for the second-highest cause of cancer death in the United States.
Shield has previously been available to doctors as a screening tool, at an out-of-pocket cost of $895. With the FDA approval, Medicare and private insurance companies are much more likely to cover the cost of the blood test, making it more widely accessible for patients.
Dr. Arvind Dasari, an associate professor in the Department of Gastrointestinal and medical oncology at the University of Texas MD Anderson Cancer Center, called the approval a “welcome development.”
But, he cautioned, “we’ll have to wait and see what the impact will be in improving screening and reducing the incidence of mortality.”
The American Cancer Society estimates that more than 53,000 people will die of colorectal cancer this year.
Research published in March showed Shield was 83% effective in finding colorectal cancers. It works by detecting the DNA that cancerous tumors release into the bloodstream.
It’s most effective in finding later-stage cancers when tumors release more of that DNA. The study found that Shield only detected 13% of earlier-stage polyps.
The test would need to be given at least every three years, starting at age 45 — the same age it’s recommended to begin colorectal screening.
A positive test isn’t necessarily a diagnosis. If the results indicate cancer is present, patients would still need a colonoscopy so doctors can see where tumors are and how far they’ve progressed.
“People have to understand that a positive Shield test requires a colonoscopy to confirm that you have an advanced lesion or colorectal cancer, or that the results were false,” said Robert Smith, senior vice president of Early Cancer Detection Science at the American Cancer Society. “A test like this is not complete if it’s positive and you have not had a colonoscopy.”
This is the second blood test to screen for colon cancer; Epigenomics’ Epi proColon was approved in 2016. But it’s rarely used, Smith said, because of concerns about its accuracy. It’s also not covered by Medicare or private insurance.
Colon and rectal cancers are increasing among people younger than 50
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