New CRC Blood Test Is Here. What Does It Mean for Screening?

 In July, the US Food and Drug Administration (FDA) approved a new 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.

A major plus for Shield is it provides a noninvasive, convenient way for patients to be screened for CRC, especially among the approximately 30% Americans who are either not being screened or not up to date with their screening.

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.

Medscape Medical News 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.

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.

What do you see as the pros and cons of this test?

Lin: The pros are that it's very convenient for patients, and it's especially easy for physicians if they have a lab in their office and can avoid a referral where patients may never get the test. However, the data I saw were disappointing, with sensitivity and specificity falling short of the stool-based Cologuard test, which is also not invasive and less likely to miss early cancers, precancerous lesions, and polyps.

Lieberman: A major con is the detection rate of only 13% for advanced precancerous lesions, which means that this test is not likely to result in much cancer prevention. There is good evidence that if advanced precancerous lesions are detected and removed, many — if not most — CRCs can be prevented.

Marshall: Another issue is the potential for a false-positive result (which occurs for 1 in every 10 tests). With this result, you would do a scope but can't find what's going on. This is a big deal. It's the first of the blood tests that will be used for cancer screening, and it could be scary for a patient to receive a positive result but not be able to figure out where it's coming from.

Will you recommend this test or rely on its results?

Lieberman: Patients need to understand that the blood test is inferior to every other screening test and, if selected, would result in less protection against developing CRC or dying from CRC than other screening tests. But models suggest that this test will perform better than no screening. Therefore, it is reasonable to offer the test to individuals who decline any other form of screening.

May: I will do what I've always done — after the FDA approval, I wait for the US Preventive Services Task Force (USPSTF) to endorse it. If it does, then I feel it's my responsibility to tell my patients about all the options they have and stay up to date on how the tests perform, what the pros and cons are, and what reliable information will help patients make the best decision.

Venook: No, but I could potentially see us moving it into surveillance mode, where CRC survivors or patients undergoing therapy could take it, which might give us a unique second bite of the apple. The test could potentially be of value in identifying early relapse or recurrence, which might give us a heads-up or jump start on follow-up.

Will patients return for colonoscopy after positive result?

Golden: This concern is relevant for all tests, including fecal immunochemical test (FIT), but I've found that if the patient is willing to do the initial test and it comes back positive, most are willing to do the follow-up. Of course, some folks have issues with this, but now we'll have a marker in their medical records and can re-engage them through outreach.

Lieberman: I am concerned that a patient who previously declined to have a colonoscopy may not follow up an abnormal blood test with a colonoscopy. If this occurs, it will render a blood test program ineffective for those patients. Patients should be told upfront that if the test is abnormal, a colonoscopy would be recommended.

May: This is a big concern that I have. We already have two-step screening processes with FIT, Cologuard, and CT colonography, and strong data show there is attrition. All doctors and companies will need to make it clear that if patients have an abnormal test result, they must undergo a colonoscopy. We must have activated and involved systems of patient follow-up and navigation.

Lin: I already have some concerns, given that some patients with positive FIT tests don't get timely follow-up. I see it in my own practice where we call patients to get a colonoscopy, but they don't take it seriously or their initial counseling wasn't clear about the possibility of needing a follow-up colonoscopy. If people aren't being screened for whatever reason in the first place and they get a positive result on the Shield blood test, they might be even less likely to get the necessary follow-up testing afterward.

What does this mean for insurance and costs for patients?

May: This is an important question because if we don't have equal access, we create or widen disparities. For insurers to cover Shield, it'll need to be endorsed by major medical societies, including USPSTF. But what will happen in the beginning is that wealthy patients who can pay out of pocket will use it, while lower-income individuals won't have access until insurers cover it.

Golden: I could do 70 (or more) FIT tests for the cost of this one blood test. A FIT test should be offered first. We're advising the Medicaid program that physicians should be required to explain why a patient doesn't want a FIT test, prior to covering this blood test.

Venook: It's too early to say. Although it's approved, we now have to look at the monetization factor. At the end of the day, we still need a colonoscopy. The science is impressive, but it doesn't mean we need to spend $900 doing a blood test.

Lin: I could see the coverage trajectory being similar to that for Cologuard, which had little coverage when it came out 10 years ago, but eventually, Medicare and commercial coverage happened. With Shield, initially, there will be some coverage gaps, especially with commercial insurance, and I can see insurance companies having concerns, especially because the test is expensive compared with other tests and the return isn't well known. It could also be a waste of money if people with positive tests don't receive follow-up colonoscopies.

What else would you like to be considered?

Marshall: These tests could pick up other genes from other cancers. My worry is that people could have another cancer detected but not find it on a colonoscopy and think the blood test must be wrong. Or they'll do a scan, which could lead to more scans and tests.

Golden: This test has received a lot of attention and coverage that didn't discuss other screening options, limitations, or nuances. Let's face it — we'll see lots of TV ads about it, but once we start dealing with the total cost of care and alternate payment models, it's going to be hard for this test to find a niche.

Venook: This test has only been validated in a population of ages 45 years or older, which is the conventional screening population. We desperately need something that can work in younger people, where CRC rates are increasing. I'd like to see the research move in that direction.

Lin: I thought it was unique that the FDA Advisory Panel clearly stated this was better than nothing but also should be used as second-line screening. The agency took pains to say this is not a colonoscopy or even equivalent to the fecal tests in use. But they appropriately did approve it because a lot of people aren't getting anything at all, which is the biggest problem with CRC screening.

https://www.medscape.com/viewarticle/crc-blood-test-here-what-does-it-mean-screening-2024a1000h4m