On July 29, the FDA approved a new screening test for colorectal cancer that requires only a blood sample.
While the test is intended to encourage more patients to get screened, its results are not perfect. The test, created by biotech company Guardant Health, was able to detect 83% of colorectal cancers in studies but only 13% of dangerous polyps, whereas colonoscopies find approximately 95% of these polyps.
Three gastroenterology leaders spoke with Becker's about the excitement surrounding a new testing option for colorectal cancers:
(Note: These responses were lightly edited for style and clarity.)
Lauren Bleich, MD. Gastroenterologist at Gastro Health (Acton, Mass.): The new FDA approval of the Shield test for colon cancer screening highlights the ongoing efforts to prevent or identify early colon cancers, which seem to be more prevalent in our younger population than ever before
This test only identified colon cancer in diagnosed patients 83% of the time, and did not identify precancerous polyps, which are removed during colonoscopy as a preventative procedure. Similar to the stool base test already approved, approximately 17% of cancers were missed by the Shield test.
While it highlights the need for colon cancer screening, as well as may allow us to reach a broader audience, especially with the long wait times for colonoscopy patients encounter, it should not be used in place of colonoscopy, which is the gold standard for colon cancer screening, and prevention.
Omar Khokhar, MD. Gastroenterologist at Illinois GastroHealth (Elgin): This was a long time coming and is exciting. Any technology that can potentially reduce the burden of colorectal cancer should be welcomed. The key points for me are:
1. Will it get more people screened? Yes.
2. Will an abnormal result lead to more downstream colonoscopy? Yes.
3. Is it perfect? No, but [it has a] similar profile to stool-based testing.
4. Is it for everyone? A resounding no. This is only for patients with an average risk profile. For high risk, colonoscopy is still the first-line option.
Benjamin Levy III, MD. Gastroenterologist at University of Chicago Medicine: I am very excited about the new Shield circulating tumor blood test, which screens for colon cancer-related DNA markers in the blood. There are many patients who would prefer blood-based screening instead of a colonoscopy or stool-based testing. The convenience of screening for colorectal cancer with a simple blood draw is pretty amazing. Gastroenterologists hope that the addition of Shield to our screening choices will help increase the number of average-risk patients getting screened nationally. The Shield test currently has a sensitivity of 83.1% for colorectal cancer. As the technology continues to improve, I hope that future generations of the Shield blood test will achieve a sensitivity of greater than 90%.
In general, gastroenterologists prefer colonoscopy as a screening modality because of the preventive medicine aspect; we can remove polyps during colonoscopy procedures and prevent colorectal cancer. However, the Shield screening blood test would be a great choice for patients who are hesitant to get a colonoscopy. Giving patients choices has the potential to help increase screening rates.
It's important for gastroenterologists and patients to check for insurance coverage because the Shield test is not yet included in the U.S. Preventive Services Task Force guidelines. Gastroenterologists and primary care physicians also need to make sure that patients are average risk before testing — and not having any alarm symptoms such as rectal bleeding, anemia or unintentional weight loss, because patients with alarm symptoms should have a diagnostic colonoscopy.
In America, only about two-thirds of our patients are up to date with their colorectal cancer screening. With increased screening through the Shield blood test, hopefully additional lives will be saved.