In July, the US Food and Drug Administration (FDA) approved the first blood-based test to screen for colorectal cancer (CRC).
The FDA’s approval of Shield (Guardant Health) marks a notable achievement, as individuals at average risk now have the option to receive a simple blood test for CRC screening, starting at age 45.
“No one has an excuse anymore not to be screened,” said John Marshall, MD, director of The Ruesch Center for the Cure of Gastrointestinal Cancers and chief medical officer of the Lombardi Comprehensive Cancer Center at the Georgetown University Medical Center in Washington, DC.
The approval was based on findings from the ECLIPSE study, which reported that Shield had 83% sensitivity for CRC and 90% specificity for advanced neoplasia, though only 13% sensitivity for advanced precancerous lesions.
While an exciting option, the test has its pros and cons.
The bad news, however, is that it does a poor job of detecting precancerous lesions. This could snowball if patients decide to replace a colonoscopy — which helps both detect and prevent CRC — with the blood test.
This news organization spoke to experts across three core specialties involved in the screening and treatment of CRC — primary care, gastroenterology, and oncology — to better understand both the potential value and potential pitfalls of this new option.
The interview responses have been condensed and edited for clarity.
What does this FDA approval mean for CRC screening?
David Lieberman, MD, gastroenterologist and professor emeritus at Oregon Health & Science University: Detecting circulating-free DNA associated with CRC in blood is a major scientific breakthrough. The ease of blood testing will appeal to patients and providers.
Folasade May, MD, director of the gastroenterology quality improvement program at the University of California, Los Angeles: The FDA approval means that we continue to broaden the scope of available tools to help reduce the impact of this largely preventable disease.
Dr. Marshall: Colonoscopy is still the gold standard, but we have to recognize that not everyone does it. And that not everyone wants to send their poop in the mail (with a stool-based test). Now there are no more excuses.
Alan Venook, MD, gastrointestinal medical oncologist at the University of California, San Francisco: Although it’s good to have a blood test that’s approved for CRC screening, I don’t think it moves the bar much in terms of screening. I worry about it overpromising and under-delivering. If it could find polyps or premalignant lesions, that would make a big difference; however, at 13%, that doesn’t really register, so this doesn’t really change anything.
Kenny Lin, MD, a family physician at Penn Medicine Lancaster General Health: I see this test as a good option for the 30% people of CRC screening age who are either not being screened or out of date for screening. I’m a little concerned about the people who are already getting recommended screening and may try to switch to this option.
William Golden, MD, internist and professor of medicine and public health at the University of Arkansas for Medical Sciences, Little Rock, Arkansas: On a scale of 1-10, I give it a 2. It’s expensive ($900 per test without insurance). It’s also not sensitive for early cancers, which would be its main value. Frankly, there are better strategies to get patients engaged.
