What do you see as the pros and cons of this test?
Dr. 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.
Dr. 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.
Dr. 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 be recommending this test or relying on its results?
Dr. 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.
Dr. 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.
Dr. 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.
Are you concerned that patients won’t return for a colonoscopy after a positive result?
Dr. 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.
Dr. 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.
Dr. 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.
Dr. 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.