Blood-Based Screening for Colorectal Cancer: Benefits and Limitations

Announcer:

This is Clinician’s Roundtable on ReachMD. On this episode, we’ll hear from Dr. Aasma Shaukat, who will be discussing circulating tumor DNA-based blood testing for colorectal cancer detection. Dr. Shaukat is the Robert M. and Mary H. Glickman Professor of Medicine and a Professor in the Department of Population Health at NYU Grossman School of Medicine. She also serves as the Director of Outcomes Research in the Division of Gastroenterology and Hepatology at NYU Langone Health.

Here's Dr. Shaukat now.

Dr. Shaukat: 

For average-risk individuals in the US, we currently have several screening options, the primary option being colonoscopy and/or a stool-based test. However, despite these options, screening rates are actually very low in the population and hover somewhere between 60 to 70 percent, so there’s a need to look for and validate additional screening modalities for average-risk individuals undergoing colon cancer screening. And in that realm, a blood-based screening test offers a lot of potential for higher adherence. There may be higher enthusiasm and uptake and that may actually boost screening rates overall. So that was the premise for undertaking a study to validate a blood-based test for average-risk colon cancer screening. 

We found that the test was quite accurate and met or exceeded the bar that has been set by Medicare for a test that it would approve, for colon cancer screening in average-risk individuals. The accuracy of the test in being able to detect colorectal cancer—the sensitivity was 79.2 percent, and the specificity was 91.5 percent. However, where the test fell short was its sensitivity for detection of advanced colorectal neoplasia or what we consider preneoplastic colorectal lesions. The sensitivity was 15.5 percent, which is lower than what we would have liked for a blood-based test because these precursor lesions are important endpoints for detection also. But overall, I think that test has good performance and is likely to be available clinically and change our clinical approach and management. 

A blood-based test may have certain advantages over colonoscopy or stool-based testing, which may actually suggest increased uptake and improved adherence. For instance, the blood test could be simply coupled with other blood tests that the patient is going to get. Most patients are used to getting their preventative care and certain labs done so the idea of coupling a screening test for colon cancer with those labs is highly appealing. Second, at the time that the provider recommends the blood test, they could actually send the patient to the lab, or the patient could schedule it right then and there so that the test is actually done. With colonoscopy it’s a separate scheduling procedure: there’s need to take time off, there’s a prep involved, so there’s a lot of different moving parts that become barriers for scheduling. And with stool-based testing, patients often get the stool kit and then they have to collect it at home, which they often forget or really don’t care to do, or they’ll sometimes lose the stool collection kit. So a blood-based test may offer some advantages in those realms, and there might be more enthusiasm from patients to undergo a screening test if it’s blood based compared to other modalities. 

Announcer:

That was Dr. Aasma Shaukat talking about the use of blood-based tests for colorectal cancer screening. To access this and other episodes in our series, visit Clinician’s Roundtable on ReachMD.com, where you can Be Part of the Knowledge. Thanks for listening!